The invention relates to premixed powder for preparing whole coarse cereal steamed bun. The premixed powder for preparing the whole coarse cereal steamed bun is prepared by mixing and processing the following materials in parts by weight: 20-40 parts of corn flour, 5-10 parts of small red bean flour, 5-10 parts of black bean flour, 5-10 parts of kidney bean flour, 5-10 parts of mung bean flour, 5-10 parts of soybean flour, 5-10 parts of black rice flour, 5-10 parts of small yellow rice flour, 5-10 parts of broomcorn flour, 5-10 parts of coix seed flour, 5-10 parts of buckwheat, 1-5 parts of sesame flour, 0.1-0.5 part of polyglycerol fatty acid ester, 0.001-0.015 part of a complex enzyme preparation, 0.1-1 part of sorbitol, 0.5-1 part of active dry yeast, 0.1-0.5 part of baking powder, 0.001-0.003 part of tricalcium phosphate and 0.5-2 parts of cross-linked pre-gelatinized carboxymethyl starch. According to the premixed powder disclosed by the invention, about 12 kinds of different types of varicolored coarse cereal flour (having five colors) of which the function and the nutrient are optimized and complementary to one another are scientifically and reasonably selected to completely replace wheal flour so as to comprehensively balance nutrient demands of human bodies, is good in taste of prepared steamed bun, and greatly simplifies the steamed bun production procedures.