For studying the effect of spontaneous emission of window on the performance of infrared detector system, we used ASAP software to simulate the spontaneous radiation of infrared detector window. The simulation results were presented in the way of equivalent black body radiation in front of the detector, and infrared detector under different temperature of black body radiation experiments were conducted to get real equivalent blackbody radiation. Through the comparison of two kinds of simulation results with experimental results, the error of the two kinds of simulation methods and the actual value were analyzed when the infrared detector detected different temperature. Finally, scheme two was suitable for the simulation of infrared detector window. Scheme two could also provide reference for the simulation modeling of other transparent optical components.