Plastic industry in the world today is one of the fastest growing industrial categories, however injection mould is one of the most rapid developing type, study to understand the plastic injection mold production process and improve product quality has great significance. This paper mainly introduces the method and the process of the injecting mold designing. First, It has introduced the position and function in the developing society of the plastic injecting mold’s making and designing, and analysied the structure of the plastic product (Chery cars threshold plaque). Next introduces the design of injection mould for plastic. Concrete design contents include: The injecting machine was chosen according to the product’s weight,the face was chosen according to the structure of the plastics and the molding parts design,the demoulding mechanism design, gating system and cooling system, etc. In addition, but also in other parts of plastic injection mould for the simple design. Through consulting relevant material, project argumetntation completed the mold design , reached the design plan descriptions of the performance requirements. This paper expounds the design of final experiences.