The compatibility analysis of the inlet and engine was conducted

according to the phenomenon of surge and stall in state of transonic speed and low-flow during flight test.The research indicates that

the instability boundaries of the engine from flight tests agree with those of the inlet from the wind tunnel tests

proving there is something wrong in the compatibility of the inlet and engine.Two methods from the perspective of the inlet and engine were presented.One was used to adjust the inlet regulation of the ramp to enlarge the instability boundary of supersonic speed and low-flow.The other was used to increase the minimum fuel flow and the nozzle area to improve the flow and the stability margin.The validated results show that the methods can relieve the problem of inlet and engine compatibility in low-flow.In future

the rules of inlet and engine compatibility in transonic low-flow state should be built.