Abstract: In order to accurately determine the contents of OPO in milk powder,infant formula samples were hydrolyzed by concentrated hydrochloric acid,and fat in samples were extracted by ethyl ether and petroleum ether,constant volume by N-hexane,with seventeen carbon triglyceride(C17:0)as internal standard,then OPO was determined by gas chromatography(GC)equipped with FID detector. The results showed that OPO was separated from other compounds very well under the GC condition,the reproducibility of the method was good,the relative standard deviation(RSD)was 1.52%,and the recovery was 90.0%~96.12%.The detection limit of this method was 20 μg/mg and the limit of quantification was 70 μg/mg. The method was accurate and stable to determine the concentration of OPO in the milk powder,supply technical support for establishment of national standard methods,product quality control and optimization and carry out OPO related research.