The maintenance work of jet molding machine focuses on the judge and shooting of troubles. It covers a wide range of knowledge and sophistication, with certain depth (such as comprehensive expertise). It requires not only the basic knowledge on the maintenance of mechanical equipment and hydraulic service, but also the basic knowledge on electric maintenance. The maintenance work of jet molding machine is hard and needs continuous study. Yet once one masters the basic working principle of jet molding machine and the basic working method, he would have the opportunity to develop a set of maintenance procedure to ensure normal working of jet molding machine.