The invention relates to a method for preparing a diabetes diet therapy medicament. A finished product prepared according to a technical scheme of the invention can cure diabetes and multiple complications. Raw materials are vinegar, black bean, Chinese medicinal herbs of rehmannia glutinosa and oriental waterplantain rhizome and the like; the black bean is fried through slow fire; after the black bean is immersed by a water decoction for 1.5 to 3 hours in a container, the vinegar is added into the container to seal the container; and the mixture in the container is taken out after two to three weeks to be dried and packed and then the finished product is obtained. The finished product prepared according to the technical scheme of the invention can adjust glycometabolism in a human body, relieve symptoms of polyphagia, polydipsia, diuresis and emaciation and the like and strengthen the immunity competence of the human body.