In the supersonic flight state of 3 Ma (1 Ma≈340.3 m/s), the temperature of the optical window heated by aerodynamics rises sharply, resulting in a large amount of infrared thermal radiation, which interferes with the imaging quality of the detector. In order to study the influence of aerodynamic thermal radiation on infrared imaging, this paper used ANSYS software to perform 3D modeling, finite element meshing and temperature field simulation on the seeker model; by using Planck's blackbody radiation formula and TracePro software, the irradiance generated by the target source and the optical window at different temperatures were calculated and simulated, and the signal-to-noise ratio model was established to analyze the influence of the temperature of the optical window and the relative distance of the target on the infrared imaging quality of the seeker. The results showed that the signal-to-noise ratio of the infrared imaging system decreased by 91.8%, 50.1%, and 20.7%, respectively after the seeker flew at an altitude of 2 km, 11 km, and 20 km for 10 seconds. The decrease of signal-to-noise ratio will seriously affect the imaging quality of the infrared system, and the cooling measures must be used to cool the optical window for reducing the interference. This paper will provide data reference for the design of the optical window of the seeker and the optical detection system, and will provide theoretical basis for the research on overcoming the interference of aerodynamic heat radiation.