Temperature characteristics of 980 nm semiconductor laser facet are analyzed. Catastrophic optical damage (COD) of semiconductor laser facet is the main reason which limits the lifetime and output power of laser. Through analyzing the heat source produced by facet, the model of facet temperature distribution is established and facet temperature field distribution is analyzed. Antireflection film and high reflection film with diamond passivation film are designed to simulate and contrast facet temperature characteristics of 980 nm semiconductor lasers with and without diamond passivation film. Simulation results show that the temperature of the former is lower than the latter of 9.0626 ℃. It can effectively reduce the facet temperature and improve the COD threshold of 980 nm semiconductor laser when coated with diamond passivation film.