Objective To develop a method to detect benzoic,sorbic acid in oily bean curd by capillary gas chromatography.Methods In alkaline condition,the samples were eliminated matrix interference by ZnSO4,extracted aqueous solution,then acidized,extracted by ether,fixed using anhydrous ethanol and finally determined by capillary gas chromatography.Results The linear range was 50-300 μg/ml(benzoic acid r=0.999 6,sorbic acid r=0.999 4).The relative standard deviation was 1.07%-3.14%,The recovery was 90.6%-101.8%.Conclusion This method is simple,rapid accurate and reliable to detect the benzoic,sorbic acid of oily bean curd.