A method for the simultaneous determination of 87 commonly used pesticides in China including 24 organophosphorous pesticides, 15 organochlorine pesticides, 12 azoles, 9 pyrethroids, 7 amides and anilines, 5 carbamates and other 15 pesticides in river water and seawater was established using solid phase extraction (SPE)-gas chromatography-mass spectrometry (GC-MS). GC-MS parameters influencing separation and sensitivity were optimized, and the effects of sample volume, pH and salinity on SPE were investigated. The purification was performed using NH2 SPE cartridge. An internal standard and 5 surrogates were used for data analysis and quality control. The results indicated that under the optimized conditions the limits of detection were in the range of 0.1 - 6.6 ng/L. For most target pesticides, recoveries were between 60% and 120% with relative standard deviations (RSDs, n = 4) of 0.01% - 9.7% at the spiked levels of 5 ng/L and 20 ng/L in real river water and sea water matrices. The method was successfully applied to monitor multi-class pesticides in surface water in Fujian Jiulong estuary, and 20 pesticides including 5 organophosphorous pesticides, 3 amides, 4 azoles, 3 carbamates, 2 pyrethroids and 3 other pesticides were detected in the mass concentration range of 1.18 - 660.93 ng/L. The proposed method can meet the requirement for the determination of trace pesticide residues in water samples.