Abstract: The quantitative measurement of infrared radiation (IR) of the attitude and orbit control rocket engine flume plays a key role in the aircraft penetration effectiveness research and in verification of the numerical simulation of the rocket engine flume flow field. In order to study the IR field of the rocket engine flume quantitatively, an experiment is conducted to measure the IR characteristics of the flume of one H₂O₂-kerosene small rocket engine. A cooled midwave infrared camera with a spectral band of 3.7~4.8 μm is developed. The detector, which has a mean NETD of 16 mK and an output resolution of 16 bits, is highly sensitive and has a wide dynamic range. With radiation calibration and calibration error analysis, the obtained grayscale images are converted, and the IR field distribution of the engine flume in the midwave infrared spectral band is acquired. The experiment result shows distinct Mach disks in the plume, and the peak radiation of the plume in the midwave infrared spectral band is 184 W/(m²·sr) with a measurement accuracy of 12 W/(m²·sr).