After the vegetable samples were cut into small pieces, an aliquot (10.00 g) was taken and mixed with 10 mL of acetonitrile by swirling for 1 min. Anhydrous magnesium sulfate (4.0 g) and sodium chloride (1.0 g) were added, the mixture was whirled for 1 min, and centrifuged for 5 min. An aliquot (1 mL) of the supernatant was taken, and 100 mg of anhydrous magnesium sulfate together with 75 mg of C₁₈ was added, respectively. After whirling for 1 min and centrifuging for 2 min, the supernatant was passed through a 0.22 μ m filter membrane. The filtrate was introduced into high performance liquid chromatograph, and targets were separated on ZORBAX SB-C₁₈ column with acetonitrile-water system at volume ratio of 45:55 under isocratic elution. As shown by the results, the mass concentrations of diflubenzuron and chlorbenzuron were linearly related with their corresponding peak areas in the range of 0.1-5.0 mg·L^-1, with detection limits (3S/N) of 0.007, 0.02 mg·kg^-1, respectively. Six repeated determinations and 6 d continuous determinations on the mixed standard solution were made, and RSDs of the peak areas of diflubenzuron and chlorbenzuron were 0.83%, 1.6% (for intra-day precision test) and 2.5%, 1.8% (for inter-day precision test), respectively. Test for the spiked recovery was made at the 3 concentration levels with cabbage, spinach and cauliflower as matrices, giving recoveries in the range of 87.4%-104% and 75.3%-98.1%. The proposed method was applied to the analysis of 15 samples of three kinds of vegetables, and diflubenzuron was detected in one cauliflower sample, and the detection amount (0.014 mg·kg^-1) was lower than the residue limit (1 mg·kg^-1) stipulated in relevant national standards.