<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-06-22</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001693664</issuerCik>
        <issuerName>ARMO BioSciences, Inc.</issuerName>
        <issuerTradingSymbol>ARMO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001487815</rptOwnerCik>
            <rptOwnerName>Cui Xiangmin</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O DECHENG CAPITAL</rptOwnerStreet1>
            <rptOwnerStreet2>35 SI NAN ROAD, 3RD FLOOR SOUTH</rptOwnerStreet2>
            <rptOwnerCity>SHANGHAI</rptOwnerCity>
            <rptOwnerState>F4</rptOwnerState>
            <rptOwnerZipCode>200020</rptOwnerZipCode>
            <rptOwnerStateDescription>CHINA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-06-22</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>U</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1214700</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Decheng Capital China Life Sciences USD Fund II, L.P.</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>39.97</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-06-22</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>18000</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.03</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2028-03-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the Agreement and Plan of Merger (the &quot;Merger Agreement&quot;), dated May 9, 2018, by and among the Issuer, Eli Lilly and Company (&quot;Parent&quot;) and Bluegill Acquisition Corporation (&quot;Merger Sub&quot;), a wholly-owned subsidiary of Parent, Merger Sub made a cash tender offer (the &quot;Offer&quot;) to purchase each outstanding share of the Issuer's common stock for $50.00 per share (the &quot;Offer Price&quot;), net to the seller in cash, without interest and less any applicable tax withholding. These shares were tendered into the Offer and, after the expiration of the Offer at one minute after 11:59 pm Eastern Time on June 21, 2018, Merger Sub accepted all of the tendered shares and the holder was entitled to receive the Offer Price per share.</footnote>
        <footnote id="F2">Pursuant to the Merger Agreement, each outstanding option to purchase shares of the Issuer's common stock, whether or not exercisable or vested, was cancelled and the holder thereof became entitled to receive an amount in cash determined by multiplying (A) the excess, if any, of $50.00 over the exercise price per share of the common stock underlying such stock option by (B) the number of shares of common stock subject to such stock option.</footnote>
        <footnote id="F3">This option, which provided for vesting in thirty-six equal monthly installments following March 31, 2018, was cancelled and the Reporting Person became entitled to receive an amount in cash per the terms of the Merger Agreement, as described in footnote (2) above.</footnote>
        <footnote id="F4">These Shares are held of record held by Decheng Capital China Life Sciences USD Fund II, L.P. (&quot;Decheng Capital&quot;). Decheng Capital Management II (&quot;Cayman&quot;), LLC (&quot;Decheng Management&quot;) serves as the general partner of Decheng Capital and possesses the power to direct the voting and disposition of the shares owned by Decheng Capital. The Reporting Person is the sole director and sole voting shareholder of Decheng Management and has sole voting and dispositive power over the shares held by Decheng Capital. The Reporting Person disclaims beneficial ownership of the shares held by Decheng Capital, except to the extent of his pecuniary interest.</footnote>
        <footnote id="F5">Each of Decheng Capital and the Reporting Person disclaim beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the &quot;Exchange Act&quot;), except to the extent of its or her pecuniary interest therein, if any. This report on Form 4 shall not be deemed an admission that any of the reporting persons is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Scott Paraker, Attorney-in-Fact</signatureName>
        <signatureDate>2018-06-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
