Abstract: Aiming at the fidelity problem of circular target simulator for simulating the infrared triangle targets such as airplane, missile and so on, a simulation technique of dynamic infrared triangle was studied. Using isosceles triangle geometrical principles ,a novel design method was proposed for isosceles triangle aperture whose size and direction were variable serially and centroid was invariable, and the dynamic triangle target with the size of 0~3and direction of 0~360was achieved. The radiation intensity from 0 to 100% for target or decoy was continuously changed by adopting a combination technique for infrared polarizer with wide spectrum. The decoy-s size and location were variable by using two-dimensional mobile platform and changeable circular aperture. The real-time control technology on Windows operating system was studied, and the main control software including Microsoft foundation class (MFC) process and real-time sub-system (RTSS) process was designed, satisfying the 500 s real-time response of control instruction. The result shows that the dynamic infrared triangle target simulator with a circular decoy can accurately simulate the infrared radiation changing process for attacking airplane or missile and releasing decoy.