Abstract: Hydrolytic degree of HPAM in water of different salinity were measured through diluted HCl titration and with a PH instrument measuring the endpoint. We focused on the measurement of hydrolytic degree of HPAM in the injected fresh water in Shuanghe oilfield, and formulated an equation between the weight of fresh water and thc volume of diluted HCl consumed, and corrected the interference with alkaline ions. This method is simple and accurate and there is no need to filtrate the samples. Experimental results show that NaCl and CaCl2 almost have no influences on the measurement of hydrolytic degree of HPAM.