Abstract: In order to quickly and accurately understand the impact on performance requirements by a number of parameters, the operating range, which is an important parameter in IR detection system, was studied in this paper. Firstly, considering the spectral transmittance characteristics of the filter and the encircled energy affected by the relative position between point spread function and the pixel, the number of electrons produced by contrast radiation intensity between target and background in the image plane was presented. Secondly, irradiance produced by both temporal and spatial noise in the image plane based on end-to-end physics performance model of IR imaging system was studied quantitatively. Considering variety of noise conditions, the operating range calculation equation was given based on the target image's signal-to-noise ratio (SNR) detection criterion. Finally, a set of MWIR staring sensor was used as an instance to calculate and analyze the operating range. By this example, it is verified that the distance calculation equation is simple and feasible. Besides, it could predict operating range of IR imaging system for different weather conditions and regions. This performance model will help the user to refine the various parameters of the IR sensor at the early design stage.