A method was developed for the determination of acephate and methamidophos in soil by ultrahigh performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) with ultrasonic extraction.10.0 g soil sample was extracted with 200 mL methanol under ultrasonic assistance for 30 min.Then the clear supernatant extract was filtered through 0.22 μm membrane,and analyzed by UPLC-MS/MS with external standard method.There were good linear relationships for acephate and methamidophos both in the range of 0.002-20.0 μg/L with their correlation coefficients(r2) larger than 0.999.The detection limits for acephate and methamidophos in soil were 0.004 9 μg/kg and 0.003 4 μg/kg,respectively.The recoveries for acephate and methamidophos at three spiked levels of 0.400,4.00 and 40.00 μg/kg were in the ranges of 83.0%-91.5% and 88.0%-94.8% with their relative standard deviations(RSDs,n=6) of 2.3%-4.8% and 1.8%-4.2%,respectively.The method was simple,rapid,sensitive and accurate in both quantitation and qualitation,and was suitable for the routine determination of acephate and methamidophos in soil samples.