The rod string is a thin rod string composed of a coupling and a rod connected by threads. The research on the dynamic behavior of the sucker rod string is the basis to prevent the failure of the sucker rod string and reduce the operation cost of the oil well. In view of the coupling vibration of rod string， it is proposed that the torsional torque generated by the friction force between the rod and tubing is the excitation of torsional vibration. Considering the influence of friction force on the coupling vibration of rod string， a simulation model of the coupling vibration of rod string in one directional well with initial bending is established under the conditions of displacement excitation at the top， load excitation at the bottom， trajectory excitation at the curved hole and tubing constraint. The four-order Runge-Kutta method is used to solve the simulation model and to simulate the dynamic behavior of the rod string. The simulation results show that： both longitudinal and transverse vibration simulation results are affected by the coupling vibration of the rod string. The effect on longitudinal vibration is not obvious. The contact force between the rod and the tubing in the inclined section of the oil well is high， and the collision in the compressed section of the rod string is serious. Hence， the inclined section of the oil well and the compressed section of the rod string are dangerous points for eccentric wear. Under norma preload conditions， the torsional vibration of the rod string is not sufficient to cause the rod string to trip. However， when the preload force of the coupling drops below the maximum torque of the rod string， torsional vibration may cause the rod string to trip.The research provides a theoretical basis for analyzing the failure mechanism of pumping rods， improving the working life of pumping rods and optimizing the design of pumping rods.