Abstract: A study on the matrix effects in the LC-MS/MS determination of 16 pesticides in 6 kinds of leaf vagetables was reported. Sample of leaf-vegetable was extracted with acetonitrile, and filtered. The filtrate was mixed with solid NaCl and an aliquot was taken for purification by passing through the SPE microcolumn (Envi-carb-NH2 column), after evaporation to dryness and dissolution of the residue in 3 mL of CH3CN+toluene (3+1) mixture. The eluates were collected and evaporated to drycess at 40 ℃ under reduced pressure and by N2-blowing in succession. The residue was taken up with methanol and made up to 5 mL with CH3OH+H2O (1+1) mixture. Standard working curves were prepared by using standard solutions of the 16 pesticides with and without addition of sample matrixes, and the matrix effects were evaluated on the base of the experimental data and values of slope ratios obtained. It was found that by applying the SPE purification with Envi-carb-NH2 column, matrix effects were eliminated in the determination of 12 among the 16 pesticides studied, and standard working curves without addition of sample matrix were used in the determinations.