The invention discloses buckwheat rice compound steamed rice with efficacy on stabilizing postprandial blood sugar and a preparation method thereof. The preparation method of the buckwheat rice compound steamed rice comprises the following steps of mixing buckwheat rice and rice to obtain compound rice; adding water into the compound rice for cooking; obtaining the buckwheat rice compound steamed rice after finishing the cooking. The buckwheat rice used in the compound steamed rice contains fagopyrin, which has a better effect on stabilizing the postprandial blood sugar, so that insulin antagonism can be prevented, and II type diabetes mellitus can be well prevented; the cooked rice has excellent taste, and has less influence on original flavor of the rice, and is suitable for dietary habit of people; the used buckwheat rice is rich in nutriments, is rich in eight essential amino-acids as well as oleic acid, linoleic acid, and other fatty acids required by a human body, and has vitamin and potassium contents higher than common rice, so that the nutritional deficiency of refined rice is greatly made up.