The objective of this research was determined of preservatives benzoic acid and sorbic acid in Namprik. Namprik were collected from local market in municipal area,Nakhonsawan province.The benzoic acid and sorbic acid were analyzed by High performance liquid chromatography(HPLC) with C-18 column.The experimental conditions were optimized and the suitable mobile phase composition was methanol – acetate buffer 0.01 M pH4.5 – 4.6 flow rate 0.7 ml/min and UV detector at 230 nm.Therefore,an understanding from this study was gained which may lead to an appropriate determination of benzoic acid and sorbic acid in food with a short analysis time,accuracy and precision