The effect of mass concentration of starch on accuracy of determining partially hydrolyzed poly acry lamide(H PAM) concentration by use of starch - cadmium iodide method was studied. The results show that the Abs not only increases with the increase of H PAM mass concent ration, but also with the increase of straight chain starch mass concentration. A way to improve the solubility of straight chain starch was adopted and the best added quantity of starch was found. The improved process for determining H PAM mass concentration was displayed. In the range from 0 to 25 mg /L of H PAM mass concentration , a standard working curve of H PAM mass concentrationvs. solution absorbency was constructed with R2 is equal to 0. 999 8.