Abstract: A Study on Quantitative Analysis of Phenyl-pyruvic Acid in Urine by GC/MSLiu Ling; Gao Wenhe; Li Guang; Han Haisheng (Laboratory of GC/MS,Tianjin Medical University,Tianjin 300070,China) Abstract:By using GC/MS, a quantitative analysis of normal children urine was made with adding different amount of phenyl-pyruvic acid and pretreating with chemical methed. The value of response of phenyl-pyruvic acid to internal standard was counted. A satisfying linear correlation shown in the figures according to relation between the value response and the amount of phenyl-pyruvic acid in urine was discussed. Keywords: phenylketonur,organic acid,quantitative analysis,GC/MS