In order to study the influence of substrate temperature on the microstructure and optical properties of ZnSe thin films， a single layer of ZnSe thin films was prepared on K9 glass substrate by electron beam evaporation. By studying the X-ray diffraction spectrum， transmission spectrum characteristics， surface morphology and roughness of the thin film， the variation rules of the microstructure and optical properties of the thin film under different substrate temperatures were analyzed. The experimental results show that the ZnSe films prepared in the range of substrate temperature from 20℃ to 200℃ are all single crystal films with （111） crystallographic texture. With the increase of substrate temperature， the kinetic energy obtained by atoms on the substrate increases， resulting in the increase of grain size， internal strain and dislocation density of the films. The optical properties of thin films are also different at different substrate temperatures. With the increase of substrate temperature， the refractive index and extinction coefficient decrease， the optical band gap increases， and the surface roughness of thin films decreases. It is concluded that the decrease of refractive index is caused by the increase of the proportion of the pores in the film， and the decrease of extinction coefficient is caused by the increase of crystallinity and the reduction of internal defects.