In order to achieve high-precision control of the rolling mill and improve product processing quality,taking the accumulator in front of servo valve in the hydraulic system of the rolling mill as the research object, the influence of the dynamic characteristics of the accumulator on the accuracy of the hydraulic screwdown position control system was analyzed.On the test rolling mill,by changing different nominal volume and charging pressure of the accumulator in front of servo valve,the influences on the hydraulic screwdown position control system were analyzed quantitatively.Finally the optimal parameters of the accumulator in front of servo valve of the rolling mill were determined.A set of selection methods for the accumulator in front of servo valve that is not limited to the hydraulic system of the rolling mill is formed.