The impact of variable geometry adjustment on performance of military turbofan engine with afterburner is analyzed and discussed.The results show as follows:During supersonic flight

increasing the nozzle throat area is an effective way to increase thrust of engine

and the higher the flight Mach number

the more remarkable the effectiveness;the nozzle throat area enlargement results in raising the surge margin of the fan effectively;the bypass ratio can be controlled by adjusting the ratio of inner and outer areas at mixer inlet

and enlarging inner area improves the performance of the engine with afterburner

but narrows the surge margin of the fan.The operating point of the fan will be optimized when the nozzle throat area and the area ratio of mixer inlet are regulated jointly and coordinately.It will be of benefit to the engine performance improvement that the pressure ratio of the fan and the mass flow increase simultaneously

while the efficiency and the surge margin of fan are kept up at a high level.