The invention relates to a Cu-Sn-Zn-S semiconductor material with an adjustable forbidden band width and a preparation method thereof, which belong to the technical field of preparing inorganic materials. The semiconductor material has a general formula of (Cu2Sn)x / 3Zn1-xS, wherein x is the mol percent content of Cu and Sn in metallic elements. The preparation method comprises the following steps of: dissolving a divalent cupric salt, a divalent tin salt and a divalent zinc salt in a polar solvent or a nonpolar solvent; adding a sulfur source into the mixture, and mixing the sulfur source with the mixture uniformly; and heating the mixture at the temperature of between 180 and 280 DEG C, and taking a deposit to obtain the semiconductor material. The semiconductor material contains no toxic elements, has very high environmental friendliness, can be prepared from a raw material with an abundant storage and a low price by a green method, and has a low cost and good repeatability; and the material has stable performance, and the forbidden band width can be adjusted between 3.5 and 0.9 electron volt. The form of the material can be nano particles, films and bulk phase material, and the material can be applied in the fields of solar batteries, microelectronic devices, environmental monitoring, pollutant disposal, biological detections and the like.