Reconstructed cooling water jacket of cylinder head of engine based on slicing method was CFD stimulated.Velocity field,pressure field,temperature field,coefficient of heat transfer and distribution situation about each water inlet were analyzed according to stimulated results,and reconstructed quality of cooling water jacket was evaluated and uneven cooling performance,local area of low velocity and backflow was found. It was optimized in order to improve its cooling performance.Stimulating results optimized before and after show that cooling performance of cooling water jacket is obviously improved by optimized project. It can be referenced for designing and optimizing cooling water jacket.