To measure the mid-infrared deuterium fluoride laser irradiance distribution, a laser beam profile diagnostic system based on uncooled mid-infrared HgCdTe photoconductive detector array is developed. Because the mid-infrared detector is very sensitive to work temperature, it is necessary to quantitatively analyze its temperature characteristics for evaluating the measuring uncertainty of the system and providing the criterion of selecting the satisfactory detector. The responsivity of HgCdTe photoconductive detector related with temperature and wavelength is analyzed. It is deduced that the responsivity can be expressed as a variable-separate function of temperature and wavelength under special conditions. The assumption is validated by the experiment，of which the responsivity of uncooled mid-infrared HgCdTe photoconductive detector in (－40~+30) ℃ is measured with 3.8 μm and 1.31 μm lasers. Based on the results, a simple and practical method to measure the temperature characteristic of the responsivity of uncooled MIR HgCdTe detector is presented.