Abstract: Regarding to the mistake that the focal plane array optoelectronic devices such as CCD were often placed on the exit port plane of integrating sphere source to perform calibration, the output irradiance uniformity of integrating sphere source was analyzed, and the basis on which the integrating sphere source was used rationally to calibrate the optoelectronic devices was obtained. Two theoretical output irradiance uniformity models based on numerical analysis method and Monte Carlo method were developed respectively. The models considered two fundamental situations of integrating sphere sources, namely ideal Lambertian source and non-ideal Lambertian source. The distribution regularity of irradiance uniformity was generalized by contrast of the theoretical data obtained by the models and the measured data obtained by two different actual integrating sphere sources. The results show that when the diameter of optoelectronic device is less than the half of the sphere exit port diameter and the ratio of the distance between device and exit port to the exit port diameter is 3~5, a 99% better output irradiance uniformity can be obtained.