In order to improve the stability of TR5 experimental terminal control system,a new control system was design and realized in 2018 both in hardware and software level.PLC(Programmable Logic Controller)is used in hardware instead of assembled PC based plug-in board.In software,several sets of control software with independent functions are integrated into one software developed by C++.After the reform of the control system,the upgraded control system has been running steadily for several months.