Zinc sulfide(ZnS) is an important infrared material because of its optical characters in 8-10 μm. It is widely used in the area of missile dome, infrared astronomical satellite, infrared spectrometer, measure instrument and thermal imager. The high temperature treatment make hot-pressed ZnS crystal develop, therefore, hexagonal ZnS and crystal pores are eliminated in the polycrystal ZnS samples. The infrared transmittance is increased. The average transmittance of post-treatment ZnS sample is 73% in the range from 2 μm to 10μm, and 60% at 1.064 μm, with 5 mm in thickness. The thermal shock resistance test results that the post-treatment ZnS reserve mechanics characters of hot-pressed ZnS before, and it make optical-electro detecting system imaging clarity through post-treatment ZnS window at 400 ℃.