The invention belongs to the field of peanut protein deep processing, and provides a formula of composite peanut protein powder. The formula is characterized by consisting of low-temperature cold-pressed semi-defatted peanut protein powder, mung bean flour, millet flour, peanut shell water-soluble dietary fiber and xylitol. The invention also provides a method for preparing the composite protein powder, which comprises the following steps of: weighing raw materials; mixing; soaking in aqueous solution; grinding into pulp by using a colloid grinder; preparing solution; homogenizing at high pressure; and performing freeze drying. The composite peanut protein powder prepared by the method has high protein content of over 40 percent through a Kjeldahl method, comprehensive and balanced nutrients, and can be drunk after being made by boiling water. Therefore, the composite peanut protein powder has the advantages of high protein content, easy solubility in boiling water, suitability for different groups, simple and easy operation of production process, suitability for industrial production and good economical and social benefits.