A method was developed for the determination of methamidophos in soil by accelerated solvent extraction/ultra performance liquid chromatography -mass spectrometry（ASE/UPLC-MS）.The experimental conditions were investigated on the basis of the optimization of ASE conditions,and the optimal conditions were obtained as follows：extraction solvent：acetonitrile,extraction temperature：80 ℃,static extraction time：10 min,cycling twice.The extraction elute was evaporated to dryness with rotary evaporator,and analyzed by UPLC-MS.The target compound was qualitatively analyzed by the external standard method,and qualitatively analyzed by MS/MS method.The linear range was 3.15-1 050 μg/kg for methamidophos,with correlation coefficient（r） of 0.999 1.The recoveries of methamidophos at three spiked levels were in the range of 72%-82% with relative standard deviations of 5.8%-8.6%.The detection limit was 0.05 μg/kg.The method showed the advantages of accuracy,good separation effect and sensitivity,and was suitable for routine sample detection.