X0508 4 2026-03-09 0001680062 ACM Research, Inc. ACMR 0001721581 Dun Haiping C/O ACM RESEARCH, INC. 42307 OSGOOD ROAD, SUITE I FREMONT CA 94539 true true Class A Common Stock 2026-03-09 4 M 0 5000 5.6 A 5000 D Class A Common Stock 2026-03-09 4 S 0 4100 43.37 D 900 D Class A Common Stock 2026-03-09 4 S 0 900 43.94 D 0 D Class A Common Stock 100000 I Dun Family GST Trust Class A Common Stock 755090 I Haiping Dun & Chi-Pin H Dun Revocable Trust Stock Option 5.6 2026-03-09 4 M 0 5000 0 D 2029-04-22 Class A Common Stock 5000 55000 D The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 13, 2025. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.88 to $43.87, 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 footnote (2) and (3) to this Form 4. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $43.90 to $44.00, inclusive. The option is fully vested and exercisable. /s/ Mark McKechnie, Attorney-in-Fact for Haiping Dun 2026-03-11