The rigidity, orientation, discharging mechanism, positioning method, gap size and other factors should be considered in the design and parameter selection of die structure. The wearing parts on the mold should be easy to replace. For plastic mold and die casting die, reasonable gating system, flow state of molten plastic or metal, position and direction of entering the cavity should also be considered. The first mock exam is to increase the productivity and reduce the runner loss. A number of identical or different products can be completed in one mold at the same time. High efficiency, high precision and long life mold should be used in mass production.