Abstract: In order to investigate the sucking performance of reciprocating pump and influence of working parameters, the sucking process of pump was simulated on the basis of Computational Fluid Dynamics. For determining the moving law of suction valve, the Adolph movement equation of reciprocating pump valve was solved with the transient inner flow field in pump, and relevant dynamic meshes were created or suspended according to the movement of piston and valve at different crank angle. Through numerical simulation, the sucking performance of reciprocating pump about transient flux, pressure contour on piston was analyzed, and the influence of stroke frequency, spring stiffness on delay-closing of suction valve was investigated. The simulation results showed that transient flux declined and absorptive capacity was 0.91 times of theoretical value for liquid compressibility and inertia. Besides, suction valve delay-closing angle increased 5.4° and delay-closing displacement increased 2.3 mm when stroke frequency raised form 100 to 330/min. The study provides a method for the liquid-solid coupling simulation of sucking performance by building the computed model adapted to the motion of piston and valve. It is useful for investigating sucking performance of reciprocating pump and optimizing the reciprocating pump.