By measuring the infrared radiation characteristics of jet airplane exhaust plume, the intensity and distribution of infrared radiation in 8~14 μm long band are obtained. Measurement results show that the exhaust plume radiant intensity at 180° direction distributes to ring and the radiation is concentrated near the engine nozzle outlet. The maximum radiant intensity and the plume area of after burner are 2.4 times and 1.3 times of non-after burner respectively. The exhaust plume radiant intensity at 90° direction distributes to symmetric envelope, the maximum radiant intensity and the plume area of after burner are 1.8 times and 2.3 times of non-after burner respectively.