Abstract: In the high sensitive infrared optical systems, the self-generated thermal radiation is one of the important factors for the detective property. Particulate contaminants are usually the main source of stray radiation. Besides the surface contaminants, there may be particulates within the detector. The influence on the luminous flux distribution on the image plane of the particulates inside the detector was studied in this paper. According to image plane's luminous flux distribution of the particulates inside detector with different temperature from different distance to image plane, relevant theoretical model was built up based on theory of infrared radiation and scattering, which was validated by the corresponding experiments. The results indicate that if there are particulates inside the detector used at the condition of vibration environment, they will form exception image such as black spot and white spot and combination with each other on the image plane. These abnormal distributions of luminous flux disturb the infrared targets in the effective field of view, resulting in false judgments. Thus, the veracity of the identification for infrared targets degraded obviously. Therefore it is of critical importance to keep the inside of the detector clean and prevent the generation of the particulates.