Injection Molding Machine (IMM) has been widely used for the mass production of a plastic product. With the development of the relative technique, various injection molding techniques have been developed and we could get more precise plastic product. In this paper, we present the system reliability of an IMM subject to a controller. The controller of an IMM is an important factor in the injection molding and this controller has direct influence on the quality of a plastic product. Presently, the mold close and open control method of a toggle type IMM is openloop control. Open-loop method is difficult to control when they affect highly nonlinear characteristic in an IMM. Therefore, we propose an alternate approach to implement the controller using closed-loop control method to enhance the reliability. Through the development, fuzzy control algorithm is selected and it is programmed by an IL(Instruction List) and a LD(Ladder Diagram) on a PC based PLC. For the development of an IMM controller, PC based PLC of PCI card type, distributed I/O modules with CANopen, Industrial PC and HMI(Human Machine Interface) software are used.