During the starting process of diesel engine, the low speed, cylinder pressure and temperature lead to spray-wall impingement and affect the fuel atomization effect. By using three dimensional calculation software Converge, the Spray-wall impingement model is established with adopting the combination of fuel spray model and B-G collision model. To verify the accuracy of the model, the visualization of constant volume bomb spray wall impinging system is designed. Based on the established Spray-wall impingement model, the influence of the background cylinder pressure, the dry and wet condition of the wall and the wall roughness on the spray wall collision of a diesel engine is simulated and analyzed. The simulation results show that: as the background cylinder pressure decreases, the collision and the oil film generation time is advanced, the diffusion distance is increased and the oil film thickness is increased. With the increase of the piston top wall roughness, the diffusion distance decreases and the oil film thickness increases. When the top wall of the piston is wet, the diffusion distance of spray oil beam increases after hitting the wall, and the oil film thickness decreases. The research provides reference for the optimized design of combustion chamber and oil injection system.