A fermentation preparation and applications of dextranase of Chaetomium globosum. A fermentation method for determining high-yield dextranase of Chaetomium globosum by optimizing medium components and fermentation conditions by means of an orthogonal experiment. The application of Chaetomium globosum in hydroglucan. The application of Chaetomium globosum in aspects of preparing drugs for preventing and treating decayed teeth or oral products. The application of Chaetomium globosum in the field of foods.