A new common-path scheme for infrared target simulator is proposed in order to simplify the structure of infrared target simulator.Based on this scheme,a dual-channel infrared projection system with compacted structure is designed.The optical system is characterized by the system field angle of ±3°,the spectral band of 3~5 mm,the entrance pupil distance of 550 mm,the focal length of 220 mm and the F number of 3.67.After analyzing the reason why the structure of the previous infrared target simulator is complex and the influence of different forms of interference target simulator structure on the design of common-path system,a good solution is given with combination of blackbody source and scanning mirror as interference target source.Through theoretical study of the influence of scanning mirror on the system performance,the feasibility of this scheme is proved.The results show that the modulation transfer function of the main target channel is better than 0.5 at the field of 16lp/mm,the root mean square (RMS) radius of each channel is less than 18 mm,and the distortion is less than 1%.The system can meet the requirements of minus 10 ℃ to 40 ℃ working environment by focusing.