Abstract: Chlorpyrifos was determined by GC-FPD after extraction by ethyl acetate using automatic solid phase extraction. Qualitative analysis was done by retention time and quantitative analysis by external standard curve. The results showed that ethyl acetate was a suitable eluent and ENVI-18 was a suitable extraction solventWhen the velocity of extraction was 2 mL/min, the extraction was optimum. The linear range of the method was 0.25~4.0 mg/L, the correlation coefficient was 0.9998, the rates of recovery were 88.6%~100.6%, the relative standard deviations were 2.58%~7.34%. The method is sensitive, accurate, be able to eliminate the interferences and suitable for determination of trace chlorpyrifos in water.