A method was established for the determination of 16 kinds of herbicides in seawater by gas chromatography-mass spectrometry(GC-MS).The samples were concentrated,purified and eluted on an HLB solid phase extraction cartridge,and the elutions were evaporated to near dryness by nitrogen blow.Then the analytes were dissolved with ethyl acetate,determined by GC-MS in selected ion monitoring mode and quantified by the external standard method.The experimental results showed that good linearities for cynazine and pendimethalin existed in the range of 4.0-200 μg/L with their detection limits of 10.0 ng/L.The other 14 herbicides showed good linearities in the range of 2.0-100 μg/L,and their detection limits were all 5.0 ng/L.The average recoveries ranged from 78.3% to 115.0% with relative standard deviations of 4.4%-9.9%.The method is simple and accurate,and is specially suitable for the detection of 16 kinds of herbicides in seawater.