The exhaust gas produced by the diesel engine is reclaimed to the mixing chamber where it was mixed with pure oxygen and argon. The mixture which forms "artificial air" will be used as the diesel intake to achieve the diesel engine’s working in closed cycle. The most critical part in closed cycle diesel engine control system is to control the oxygen concentration and specific heat of the intake. This paper is based on the design of GE9030-based PLC and the monitoring interface used in this paper is designed by KingView6.53, finally, the control of specific heat of the intake, concentration of the oxygen intake and pressure of the intake are realized. Moreover, real-time displaying, gathering and fault alarm of the operating parameters in this system are achieved.