By KrF pulsed excimer laser deposition (PLD), the high quality diamond like carbon (DLC) films have been deposited on ZnS substrate to improve its environment reliability. The plasma excited by the laser is also analyzed. And the helpful particles in plasma are filtered and deposited. The adhesion strength of DLC film with ZnS substrates was improved without narrowing the spectral range and decreasing the transmission. The uniformity of films is improved to 95% in 80 mm area by off-axis rotating-substrate method. The spectral range of DLC/ZnS sample is 0.53～12 μm, especially the transmission is higher than 70% in the spectral range of 1.3～11 μm, moisture-resistance is 95%～100%, and working temperature is -45～85 ℃. The adhesion strength has achieved requirement of “General specification for optical coatings” (GJB2485-95). The research shows that the environment reliability of ZnS has been improved obviously by depositing DLC film.