The most commonly used method to detect melamine content in dairy products is high performance liquid chromatography（HPLC）in GB/T22388—2008 method for detecting melamine in raw milk and dairy products. When using high performance liquid chromatography for analysis,the type and proportion of mobile phase have great influence on the test results,especially on the peak time,peak area,peak type and recovery rate. Therefore,it is extremely important to configure the appropriate mobile phase ratio for obtaining good atlas and results. In this paper,the ratio of ions to reagents and acetonitrile in mobile phase was taken as variable,and the influence of the ratio of 85:15,88:12,90:10,92:8 and 95:5 on the test results was explored,and the most suitable ratio of mobile phase in the current laboratory environment was found out,so as to improve the reliability of the test results.