Abstract: The fishpond water samples were extracted with fully automatic online HS-SPME. Temperature of extraction was 75℃, time of extraction was 60 min, adding amount of sodium chloride was 0.3 kg·L^-1 and sample volume was 2.0 mL. GC-MS/MS was applied to the determination of endosulfan(α-endosulfan and β-endosulfan) and endosulfan sulfate in water samples. The DB-5 ms capillary chromatographic column was used for GC separation and the multiple reaction monitoring mode was adopted in MS/MS determination. Linear relationships between values of peak area and mass concentration of α-endosulfan, β-endosulfan, and endosulfan sulfate were kept in definite ranges, with detection limits (3S/N) in the range of 0.001-0.015 μg·L^-1 and lower limits of determination (10S/N) in the range of 0.003-0.050 μg·L^-1. On the base of blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 83.6%-117%, with intra-day RSDs (n=6) of determined values in the range of 2.2%-18% and inter-day RSDs (n=3) in the range of 4.2%-18%.