A method was developed for the overcoming matrix effects in gas chromatography analysis of organophosphorus pesticide residues in vegetable by using L-gulonic acidγ-lactone as a masking reagent.Effects of overcoming matrix effects while using L-gulonic acidγ-lactone were investigated.The result indicated that the addition of 1.0 g/L L-gulonic acidγ-lactone could significantly improve the chromatographic behaviors of susceptible pesticides，such as methamidophos，acephate，omethoate，moncrotophos，on gas chromatography，the peak intensities of four pesticides were 2.8,9.1,10.4 and 4.8 times higher than those in acetonitrile，respectively.There were no negative effects on the chromatographic behavior of unsusceptible pesticides（e.g.chlorpyrifos and parathion）.Five 0.25 mg/L standard solutions with the addition of masking reagent were injected at the beginning and every 25 samples in the sequence（100 GC injections）.The RSDs for peak heights and peak areas of five injections were 2.4％-11.8％ and 4.3％-7.5％，respectively.The average recoveries of the selected pesticides were between 80％ and 120％ with RSDs of 1.6％-13.5％.The method was simple and effective，and could be used to overcome matrix effects in GC analysis of organophosphorus pesticide residues in vegetables.