The invention discloses a two-dimensional transition metal chalcogenide film and a preparation method thereof. The preparation method comprises the steps that A and B are mixed and then added into a C solution, and thus a precursor solution is obtained, wherein A is molybdenum pentachloride or tungsten tetrachloride, B is thiourea or selenourea, and C is isopropanol, or ethyl alcohol or methyl alcohol; the precursor solution is smeared on a silicon wafer with an oxidation layer; and a precursor placed on the surface of the silicon wafer is irradiated by a laser with the output power being 20-200 W for 0.02-2 s under the vacuum environment or the inert atmosphere environment, and thus the two-dimensional transition metal chalcogenide film is obtained. According to the preparation method, the two-dimensional transition metal chalcogenide film is prepared through a laser, the technological process is simple, the two-dimensional transition metal chalcogenide film with the high quality can be obtained in a short time, and the preparation method is suitable for large batch production of the two-dimensional transition metal chalcogenide films.