X0508 4 2025-09-18 0001680062 ACM Research, Inc. ACMR 0001721279 Cheav Sotheara C/O ACM RESEARCH, INC. 42307 OSGOOD ROAD, SUITE I FREMONT CA 94539 true See remarks true Class A Common Stock 2025-09-18 4 M 0 10000 13.89 A 110002 D Class A Common Stock 2025-09-18 4 S 0 10000 35 D 100002 D Stock Option 13.89 2025-09-18 4 M 0 10000 0 D 2033-08-09 Class A Common Stock 10000 56250 D On September 18, 2025, the reporting person exercised a previously issued stock option to purchase 10,000 shares of Class A Common Stock of the Issuer. The sale reported in this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 15, 2025. The option will vest and become exercisable as to 7,500 shares on May 15, 2026 and the remaining 22,500 shares will vest and become exercisable in equal monthly installments over the following 36 months, subject to continued service through each vesting date. option is fully vested and exercisable. Senior Vice President, Manufacturing of ACM Research (Shanghai), Inc., a subsidiary of the Issuer. /s/ Mark McKechnie, Attorney-in-Fact for Sotheara Cheav 2025-09-19