X0306 4 2021-08-23 0001680062 ACM Research, Inc. ACMR 0001721583 Xiang Yinan C/O ACM RESEARCH, INC. 42307 OSGOOD ROAD, SUITE I FREMONT CA 94539 true Class A Common Stock 2021-08-23 4 S 0 35136 85.0286 D 1390799 I See footnote Class A Common Stock 2021-08-24 4 S 0 33000 86.0762 D 1357799 I See footnote Class A Common Stock 2021-08-24 4 S 0 200000 88.1087 D 1157799 I See footnote Class A Common Stock 2021-08-24 4 S 0 11629 88.9702 D 1146170 I See footnote The sale reported on this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by Shanghai Science and Technology Venture Capital Co., Ltd. The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $85.00 to $85.28, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes 2 and 4 of this Form 4. These shares are owned by Shanghai Science and Technology Venture Capital Co., Ltd., which designated the reporting person to the board of directors of the Issuer. The reporting person disclaims beneficial ownership of the shares owned by Shanghai Science and Technology Venture Capital Co., Ltd. except to the extent of her pecuniary interest therein, and this report shall not be deemed an admission that such reporting person is the beneficial owner of such securities for purposes of Section 16 or otherwise. The price reported in Column 4 represents a weighted average price. The shares were sold in multiple transactions at prices ranging from $87.80 to $88.37, inclusive. /s/ Mark L. Johnson, Attorney-in-Fact for Yinan Xiang 2021-08-24