The crank-slider mechanism is the key component in reciprocating pumps. With the increase of the rotational speed of the crank-slider mechanism, the vibration and working noise of reciprocating pumps increase. Based on the multi-body dynamics theory, the dynamic model of the crank-slider mechanism of reciprocating pumps is proposed. A numerical example is given and the validity of the procedure developed here is demonstrated by analyzing the dynamic behavior of a typical crank-slider mechanism of the reciprocating pump. The model can well simulate the dynamic response of the mechanism, which can enable designers to obtain required information on the analysis and design of reciprocating pumps.