The invention relates to a high-quality tin-germanium-sulfur selenide film prepared by simultaneously increasing the Ge content and the sulfur and selenium partial pressure. The Ge content is the relative ratio (Ge/(Ge+ Sn)) of Ge and Sn in tin-germanium-sulfur selenide (M1x1M2x2Sn1-xGexS1-ySey) (M1 is a mixture of one or two of Cu and Ag at an optional ratio, M2 is a mixture of one or two of Zn and Cd at an optional ratio, x1 is greater than or equal to 0 and less than or equal to 1, x2 is greater than or equal to 0 and less than or equal to 1, x is greater than 0 and less than or equal to 1, and y is greater than or equal to 0 and less than or equal to 1; and sulfur and selenium partial pressure is partial pressure of simple substance S steam, simple substance Se steam, H2S gas or H2Se gas in a sulfoselenide treatment process. By simultaneously increasing the Ge content and the sulfur and selenium partial pressure, the photoelectric property of the tin-germanium-sulfur selenide film is greatly improved. The method is simple to operate and has universality; and the prepared high-quality tin-germanium-sulfur selenide film can be applied to photoelectric devices such as solar cells, photoelectric water cells, photoelectric detectors and the like.