Abstract: On the basis of the luminance contrast between target and background, the model of luminance fusion under the condition of infrared irradiation was established and then the condition of luminance fusion was obtained. According to different combinations of target and background in infrared detection, the applicable objects under the condition of infrared irradiation were studied and the conclusion was verified through the simulation of different combinations. The results show that the method of realizing the luminance fusion by infrared irradiation is suitable for bright objects with higher emissivity and dark objects with lower emissivity than background. Especially, when target's temperature is equal to background's, the infrared radiation realizing the luminance fusion on one band is equal to the radiation remittance of blackbody with the same temperature on the same band. In the end, the experiments were carried out with real infrared irradiating system irradiating different combinations of target and background, including bright target and dark target. Experimental results show that the luminance fusion of target and background has been realized on the middle infrared band to a certain extent, illustrating the effectiveness of the proposed method.