Metering pump is a displacement reciprocating pump, with unique metering and conveying function, it is a modern process of the necessary high-precision conveying equipment. At present, domestic and foreign metering pump products mostly use gravity ball valve, and domestic for the impact of gravity ball valve on measurement accuracy, experimental research work is seriously lagging behind, leading to domestic high-precision measurement products have always been dependent on imports. The dynamic characteristics of impact effect and widmanstatten liquid can not be compressed based on valve movement of liquid in the cylinder and the continuous flow conditions of pump valve motion, the differential equations are established. The motion rule of valve. The computer simulation program of pump valve motion is compiled, and the numerical simulation calculation is carried out with this pump. The influence of the lag angle of ball valve on measurement accuracy is further analyzed. The definition and the factors affecting the accuracy of two and 1, the definition of metering pumps metering accuracy refers to the external conditions prescribed, for the same traffic flow indication multiple independent measurements, repetition degree of every measured value, or is the discrete degree measurement. In numerical value, the relative error of limit can be used to express the smaller value, that is to say, the measuring accuracy is high.