The invention discloses health-care food for patients who suffer from diabetes and a preparation method thereof. The health-care food is prepared from the following components by mass: 35 to 50 grams of fagopyrum tataricum gaerth seeds, 20 to 40 grams of fagopyrum esculentum moench seeds, 15 to 25 grams of dioscorea opposita thumb and 5 to 15 grams of black soybeans. The preparation method comprises the following steps of: 1, drying fagopyrum esculentum moench in the sun, unshelling, and removing impurities to obtain the fagopyrum esculentum moench seeds, and storing into a drying storehouse for later use; 2, cleaning the dioscorea opposita thumb, peeling, cutting into granules with the sizes of broad beans, steaming to be cooked, drying in the sun, and storing into the drying storehouse for later use; 3, selecting the black soybeans, drying in the sun, and storing into the drying storehouse for later use; 4, mixing uniformly in a mass ratio, crushing, and screening, taking powder below half of a millimeter as flour, and adding appropriate seasonings into the flour to process a noodle series; and screening the residual granules, and sealing the granules with the sizes of about 2 millimeters and bagging. The health-care food is prepared by processing natural raw materials, has the effects of reducing blood sugar and blood fat, enhancing the immunity of human bodies, benefiting lung, nourishing stomach and the like, is safe and non-toxic and can be eaten for a long time.