The cooling water jacket is one of the main cooling components of the engine cooling system. The reasonable design of the water jacket structure has an important impact on the engine performance. The cooling water jacket is mainly composed of cylinder head water jacket, cylinder pad and cylinder body water jacket. The nose area of the cylinder head water jacket is a high temperature area, and the heat generated needs efficient cooling to ensure its heat dissipation performance. In order to evaluate the rationality of water jacket structure design and systematically analyze the flow characteristics of coolant in water jacket, the CFD analysis software star-ccm + is used to conduct the numerical simulation of an engine cooling water jacket, and an improved cooling water jacket structure method based on flow path is proposed. Through the numerical simulation of the coolant flow path and velocity distribution uniformity, it can effectively optimize and improve the insufficient coolant flow of the existing cooling water jacket, and significantly improve the nose bridge area and exhaust side area The overall cooling performance of the cooling water jacket is improved by the cooling of the cooling zone. The CFD simulation and structure improvement method of cooling water jacket based on flow path can provide theoretical guidance for the design and optimization of engine cooling water jacket.