Abstract: A gas chromatohraph-mass spectrum method was established for determination of atrazine in seawater and sea food. The pretreatment and chromatographic conditions were optimized. The total of 50 mL dichloromethane was chosen in the process of organic solvent-seawater extract with liquid-liquid extraction technique. Florisil SPE column and hexane mixed with ethyl acetate were used to clean up the sea food sample so as to reduce continuum organic interference in GC-MS detection. Identification was achieved by Electron Ionization mode (EI) using select ion monitoring (SIM). Under the optimal conditions,good linearities were obtained for atrazine in the range of 0.001~0.5 μg/L. The quantification was performed with internal standards. The recoveries of atrazine in seawater and sea food were in the range of 95.8%~113.2% and 83.1%~92.6% respectively. The relative standard deviations (RSD) were less than 4.4%. The limits of detection were 0.001 μg/L for atrazine in seawater, and 0.001 mg/kg for atrazine in sea food. The method has been successfully applied to determination of atrazine in seawater and sea food in sea area of Fujian province during an accident.