Abstract: Electric propulsion system includes complex interfaces,hardware and software are strong coupling,high reliability is required,and whole designs difficulty.This paper introduces the prototype development of sub-kW ion electric propulsion subsystem,which mainly includes the composition of the subsystem,product designs,reliability verification,and system joint tests etc.To incorporate electrical equipment from the system architecture,the interface optimization goal is realized.The FDIR functions are decomposed to three levels:hardware,main control software and FDIR software,realizing fault redundancy and optimal.The system has achieved dual-ignition and closed-loop thrust control.System thrust is 80 mN,the specific impulse is 3 000 s,and the power is less than 2 370 W.