A method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was established for the determination of pyriproxyfen residue in vegetables and fruits. The pyriproxyfen residue in the sample was extracted by acidified acetonitrile with the presence of sodium acetate buffer, and cleaned up by PSA (primary secondary amine) sorbent, and the separation was performed by ultrafast liquid chromatography (UFLC) on a CAPCELL PAK C18 column (50 mm x 2.0 mm, 3 microm) and the gradient elution of acetonitrile (containing 0.1% formic acid) and 2 mmol/L ammonium acetate solution (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. The calibration curve was linear between the peak area and the con centration of 2.5 - 50 microg/L with the correlation coefficient more than 0.9999. The limit of quantification of pyriproxyfen was 5 microg/kg. The average recoveries spiked at three concentrations of 5, 50 and 100 microg/kg ranged 84.7% -91.5%. The relative standard deviations (n = 10) were all less than 10%. The method is selective without interference and suitable for the determination of pyriproxyfen residue in vegetables and fruits.