The accurate acquisition of optical constants of SnTe nanofilm is of great significance for the design of high-performance optoelectronic devices and their potential applications in the field of optoelectronics. However, there are still few reports about the methods to obtain the optical constants of the nanofilm. SnTe nanofilm was prepared on quartz substrate by magnetron sputtering with a SnTe single target. Under the conditions of with no heating of the substrate and annealing treatment, using the appropriate process parameters, a crystalline and compositionally controlled face-centered cubic SnTe nanofilm has been obtained. The thickness, composition, refractive index, extinction coefficient and other optical constants of SnTe nanofilm were studied by using spectral ellipsometry (SE). Different fitting model structures were established. SnTe material data lists in SE database and the Tauc-Laurents model were used for fitting analysis respectively. The results show that the SnTe nanofilm with such thickness has a higher refractive index in the visible band and a wider spectral absorption from visible to near infrared.