The invention discloses a preparation method of an oxidization film in a surface of silicon carbide. The method comprises the following steps of 1) cleaning a silicon carbide material (10) containing a substrate (11) and an epitaxial thin film (12); 2) performing oxygen plasma processing on an upper surface of the epitaxial thin film (12); 3) pre-processing a sample (13) obtained in the step 2) in a high temperature; and 4) oxidizing a sample (14) obtained in the step 3) to obtain the oxidization film (15). According to the method, by passivation on the surface of the silicon carbide before formation of the silicon carbide oxidization film, the quality of the silicon carbide oxidization film is improved, and the silicon carbide/silicon dioxide interface state density is reduced; and the method is simple and practical and is suitable for industrial production on a large scale.