Abstract: By optimizing the extraction and purification conditions, the method mentioned by the title was proposed to determine 7 nematocides in soil samples, including dazomet, fosthiazate, ethoprophos, fensulfothion, oxamyl, fosthietan and dichlofenthion. Soil sample was collected randomly, dried by air, crushed and sieved. An aliquot (10.0 g) was taken, and 15.0 g of diatomaceous earth was added. The mixture was extracted automatically under heating and pressure conditions with the mixed solution of methanol and trichloromethane at volume ratio of 2∶1. The extract was passed through the activated HLB solid phase extraction column for elution by 10 mL of the mixed solution of methanol and acetonitrile at volume ratio of 1∶1. The eluent was blown to near dryness by nitrogen at 45 ℃, and the residue was dissolved in 1 mL of ethyl acetate. The solution obtained was passed through a 0.22 μm filter membrane, and the filtrate was determined by ultra-high performance liquid chromatography-tandem mass spectrometry. It was shown that linear relationships between values of the mass concentration and the peak area of the 7 nematocides were kept in the range of 0.005-2.0 mg·L^-1, with detection limits (3S/N) in the range of 4-25 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 87.2%-101%, and RSDs (n=6) of the determined values in the range of 1.5%-3.8%. The proposed method was used for the analysis of actual samples, and dazomet, fosthiazate, ethoprophos, fensulfothion and dichlofenthion were detected with detection amounts ranged from 14.81 μg·kg^-1to 124.03 μg·kg^-1.