Abstract: A method of multiresidue simultaneous determination of twelve acid herbicides in rice was described.The method involved extraction using acetone and acid water solution(150∶20,V/V),and the herbicides isolated on the DB-5MS and derivatization with dizomethane were determined with internal standard(IS) method by selected-ion monitoring(SIM) mode using gas chromatography-mass spectrometry(GC/MS).The extraction was partitioned with acetic ester,cleaning up with gel permeation chromatography(GPC).Recoveries of ten herbicides were more than 80%,and relative standard deviation(RSD) was less than 10%.The determination limit range: 0.01-0.05 mg/kg.