Bearing is one of the most critical and the most vulnerable parts of mechanical transmission system,Accurate identification of its faults is the key to achieve stable operation of equipment. The five degree of freedom dynamic model of rolling bearing system with local fault is established by considering the nonlinear factors such as oil film and the sliding of rolling element. An improved model of pitting failure is proposed, and the corresponding models of different fault parameters are analyzed. The system vibration signal of the inner ring and the outer ring with pitting fault is simulated, and the corresponding fault characteristics are analyzed. Through the comparative analysis of the simulation signal and experimental signal, the correctness of the model is verified, which can help to realize the early diagnosis of bearing fault.