Abstract: Distributed Aperture Infrared System(DAIRS) is the trend of infrared search and track system of military powers. Operation range is one of the most important parameters of DAIRS, which is decided by system parameters, features of target and background, etc. The operation range based on the characteristics of imaging and information processing of DAIRS was studied in this paper. A mathematical model of operating range for ground-based DAIRS was established, and the influences of target orientation, detector integration time, and instantaneous field of view(IFOV) on operation range of DAIRS and traditional scanning imaging infrared system were analyzed. The mathematical model is helpful to the design of DAIRS.