The commonly used children's tricycle mould steels are 45#, 40Cr, P20, 2738, 2316, 718, NAK80, S136, etc. Generally, we suggest to use steel 718 and Shanghai Baosteel P20. Good mold structure design is the premise of a qualified mold manufacturing. The mold structure and product structure should be analyzed in all aspects, including mold draft angle, miniature of product surface, design of pouring system, design of exhaust system, design of cooling system, etc. The most important and most likely problems of these molds will be repeatedly tried in the mold structure design Proven.