The invention relates to selenium-rich nutritional powder and a preparation method thereof and belongs to the technical field of health-care food. The selenium-rich nutritional powder is prepared from the following raw materials in parts by weight: 100-120 parts of black peanut powder, 40-60 parts of black corn flour, 20-40 parts of black sesame seed powder, 50-80 parts of wheat flour, 30-45 parts of buckwheat flour, 20-30 parts of kudzu root starch, 10-15 parts of nut kernel powder, 10-20 parts of Potentilla anserina powder, 8-12 parts of lycium barbarum and 5-9 parts of wild jujube seeds. According to the selenium-rich nutritional powder provided by the invention, raw materials such as black peanuts with very high selenium content are adopted as main ingredients, traditional Chinese medicine powder serves as an auxiliary ingredient, and organic selenium in the selenium-rich nutritional powder can be used for cleaning in-vivo free radicals, expelling in-vivo toxins, resisting oxidation, effectively inhibiting the generation of lipid peroxides, preventing blood clots, clearing cholesterol, improving human immunologic function and can also be used for protecting liver and expelling toxins; the selenium-rich nutritional powder can be directly swelled by boiling water and can also be added into wheat flour so as to prepare steamed bread, bread, cakes and pastries and the like.