A gas chromatography-mass spectrometric（GC-MS）method was developed for the simultaneous determination of 4 kinds of antifouling biocides，including chlorothalonil，dichlofluanid，Sea-Nine 211 and Irgarol 1051 in marine coatings.The samples were extracted by ultrasonic method using ethyl acetate as solvent at room temperature，and the solid impurities were removed from the solution through the organic membrane，and then the target compounds were determined by GC-MS in selected ion monoitoring mode（SIM）.Under the optimal conditions，The standard calibration curves of chlorothalonil，dichlofluanid，Sea-Nine 211 and Irgarol 1051 were linear over the assayed range with correlation coefficients higher than 0.99.The detection limits（LOD，S/N≥3） ranged from 0.3 mg/kg to 1.3 mg/kg，and the limits of quantitation（LOQ，S/N≥10） ranged from 1.0 mg/kg to 4.3 mg/kg.The recoveries of the analytes in spiked samples ranged from 82.6% to 109.9%，with relative standard deviations（RSDs） less than 5%，The proposed method was applied in the determination of antifouling biocides in 6 commercially available marine antifouling coatings，and two of which were detected containing chlorothalonil，dichlofluanid and Sea-Nine 211，respectively.The method could meet the requirements for rapid and accuate determination of 4 antifouling biocides in marine coatings.