The invention discloses a preparation method of nutrition formulation millet powder for old and middle-aged people. The preparation method comprises the following steps: weighing millets, millet sprouts and spirulina, mixing, cleaning, arranging the cleaned mixture into a steam explosion vessel, carrying out steam explosion, arranging the mixture subjected to steam explosion into an enzymatic vessel, carrying out enzymolysis for 72 hours, embedding and debitterizing yak milk casein peptide powder, mixing the embedded and debitterized yak milk casein peptide powder and the obtained enzymatic hydrolysate, then arranging into a double-layer stainless steel stirring kettle with automatic heating function, sequentially adding purple sweet potato anthocyanidin starch, fruit and vegetable cellulose powder, deep sea fish oil, soybean protein isolate and fennel powder, heating and stirring for 33 minutes, then adding vitamin A and vitamin D, further stirring for 15 minutes, discharging, naturally cooling to room temperature to obtain a mixture, carrying out homogenization on the mixture obtained in the step S3, and then carrying out spray drying to obtain a finished product. The millet powder has a high nutrition value, is rich in dietary fiber, is beneficial to promoting the gastrointestinal peristalsis of the old and middle-aged people, and can be used for enhancing the digestive ability, preventing constipation, and improving the immunity after being taken for a long term.