A model of reciprocating seal was built by finite element analysis software.The variation of the seal inner diameter under different spring stiffness was simulated, the effects of spring stiffness coefficient, interference fit and rod speed on seal sealing performance were studied, and the heat generation and pumping rate were calculated. The result indicates that, there is a liner relationship between the spring stiffness coefficient and the seal inner diameter; As the interference fit increases, the oil film thickness is increased during the instroke, and it almost remains the same during the outstroke, which leads the increase of the pumping rate; The heat generation is increased and the temperature in the seal lip is also increased along the increase of interference fit; Both the heat generation and pumping rate are increased as the rod speed increases.