Abstract: Simulation modeling of sucker rod string’s longitudinal vibration is the basis for efficiency simulation of the pumping well system and optimization design of the swabbing parameters. In view of the fact that the current simulation models of longitudinal vibration of the sucker rod string do not consider the influence of gas-liquid separation in pump on the bottom boundary conditions of the longitudinal vibration of rod string, a simulation model of the pressure in pump is established based on the continuous flow equation to improve the bottom boundary conditions of the longitudinal vibration of rod string, and that of the coupling between the pressure in pump and the longitudinal vibration of sucker rod string is further established. The simulation model is solved by a hybrid algorithm of spatial dispersion and continuous time and fourth-order Ronge-Kutta method, thus achieving the simulation calculation of the longitudinal vibration of sucker rod string. The accuracy of the simulation model is verified by comparing the diagram of simulated power with that of measured power. The simulation results show that the fluid gas-liquid separation in pump significantly affects the longitudinal vibration of the sucker rod string:(1)After considering the gas-liquid separation phenomenon, the loading and unloading speed at the suspension point and plunger is faster, and the longitudinal vibration of rod string is more obvious. (2)The higher the well stroke number and larger the pump diameter, the more obvious the impact of gas-liquid separation on the longitudinal vibration of rod string; the higher the well sinkage, the lower the water content, and the larger the production gas-oil ratio, the more obvious the impact of gas-liquid separation on the longitudinal vibration of rod string. The results of the study can further improve the accuracy of efficiency simulation model for the pumping well system.