In order to study the mechanism of the vibration of coke pushing device， a two-degree-of-freedom friction self-excited vibration model is established. The critical instability speed of the coke pushing system is obtained by the Lyapunov stability theory， and the stability of the system is analyzed. The stick-slip speed of the coke pushing system is obtained by theoretical calculation， and the stick-slip motion of the system is analyzed. The theoretical calculation results are verified by analyzing the stability and stick-slip motion of the system with different excitation speeds. In view of the influence of the dynamic and static friction coefficients on the stability and stick-slip motion of the coke pushing system， the phase diagrams and Poincare sectional views of the system with different friction coefficients are obtained by numerical simulation. The speed response curves of the coke pushing device with different friction coefficients are also obtained by using the virtual prototype technology. The results show that the decrease of the difference of dynamic and static friction coefficients is beneficial to the improvement of the stability of coke pushing system， but it cannot improve the stick-slip motion of coke pushing device.