Considering the IR radiation space distribution research of fight plane is very little, in order to deeply understand IR radiation space distribution characteristics of fight plane in 3-5 μm, the infrared radiation ellipsoid model of tail flare is established, IR radiation characteristics of fight plane in different directions in 3-5 μm are simulated and calculated with the fight plane skin IR radiation model and the tail nozzle IR radiation model, and space distribution curves of IR radiation is given. The calculation shows that the infrared radiation of the aircraft is symmetrical with respect to the wing plane and the longitudinal symmetry plane of the fuselage. There are 4 extremes each in the tail and nose. The maximum value of infrared radiation is 5 177 W when the radiation direction is （ $ \pm $150°, $ \pm $32°） in the tail and the maximum value is 3 461 W when the radiation direction is ( $ \pm $68°, $ \pm $64°) in the nose. By analyzing the distribution rule of IR radiation of fight plane in the wing plane, the fuselage longitudinal symmetrical plane and the peak value plane, the IR radiation is very low when the radiation direction is positive direction of the plane axis, and the IR radiation grows rapidly when the angle between the radiation direction and the plane axis increases and the radiation direction is not positive direction of the plane axis. The research also shows the direction of peak value of IR radiation is closer to the plane axis in longitudinal symmetrical plane if the angle between the projection of radiation direction in wing plane and the plane axis becomes small. Similarly, the direction of peak value of IR radiation is closer to the plane axis in wing plane if the angle between the projection of radiation direction in longitudinal symmetrical plane and the plane axis becomes small.