Abstract: Carbofuran, acetochlor, alachlor, metolachlor and trifluralin in soybean were determined by gas chromatography-mass spectrometry(GC/MS) with electron impact(EI) ionization. The soybean samples were extracted with acetonitrile. The pigment and lipin were cleaned up with GPC. Carbofuran, acetochlor, alachlor, metolachlor and trifluralin were analyzed by GC/MS with selected-ion monitoring(SIM). The results showed that GPC purification could avoid the influence of lipid collected time between 5 and 15 min. The recoveries of those pesticides are ranged from 66.2% to 104.9%, and standard deviations are from 2.2% to 12.3%. Under the optimized conditions, the calibration curves of 5 pesticides are linear in the range of 0.01—0.1 mg/L with correlation coefficients more than 0.996. The limits of quantitation of carbofuran, acetochlor, alachlor, metolachlor and trifluralin are 0.01 mg/kg.