This article describes the PLC temperature monitoring system based on MCGS, including its composition, working principle, PLC program design and debugging, MCGS configuration, system debugging and so on. Monitoring system's design eliminates the shortcomings of the PLC control system that it is unable to visually show the parameter changes on the scene. Thus by this design, the operators can monitor real-time parameters and set the parameters of the process flows. Thus operation and maintenance is more convenient.