To investigate the matching principle between supersonic inlets and gas turbine engines and to improve the installed performance of supersonic propulsion systems, a simplified method to simulate the supersonic inlet installed performance in terms of engine and inlet matching was developed. This method was based on quasi one dimensional simulation of the flow field of supersonic inlets and the component-based gas turbine engine performance simulation model. Consequently, it is capable of simulating the installed drag of supersonic inlets on different flight and working conditions. This method was validated using data from other references before it was used to investigate the matching between '2+1' supersonic inlet and a turbofan engine during subsonic cruise and the performance of a variable supersonic inlet. Results show that, the deviations of inlet pressure recovery and mass flow coefficient are within 1.4%, while the deviations of installed performance of some turbofan engine is within 9%. Noticeable additive drag was detected during subsonic cruise when the engine was working in deep throttle conditions. Variable inlet can reduce the spillage drag and increase the stability of supersonic inlet at high flight Mach numbers. © 2017, Editorial Department of Journal of Propulsion Technology. All right reserved.