The invention discloses a variable band gap AlCoCrFeNi high-entropy alloy oxide semiconductor film and a preparing method thereof, and belongs to the technical field of semiconductor materials. The film has the following general formula: (AlCoCrFeNi)1-xOx, wherein x is equal to 0.3-0.7, y is equal to 0-1.0, and the atomic ratio of Al:Co:Cr:Fe:Ni of a magnetron sputtering target material is y:1:1:1:1. The film is in a nanocrystalline or amorphous state, and integral oxidization is achieved. Through adjustment of x and y, the band gap width can continuously change in the section of 2.20-4.20eV, the hardness can continuously change in the section of 7-20 Gpa, the specific resistance can continuously change in the section of 1 x 10<7>-1 x 10<19> mu omega.cm, and films growing on differentmatrixes show transparency or different colors. The method for film preparing through a magnetron sputtering method is mature, the nanocrystalline or amorphous state structure can be obtained, integral oxidization is achieved, the film is uniform and dense, and the surface is flat. According to the film, flexible selecting and changing of metal elements or changing of oxygen partial pressure is conducted for wide-range adjustment, wide-range adjustment of properties (band gap width, hardness, specific resistance, colors and the like) can be brought, the application field of the film is widened, and the film can be applied to the fields of optics, microelectronic devices, high-hardness abrasion resisting and decoration films and the like.