The invention discloses a preparation method of high-nutrition instant soybean milk powder, and belongs to the processing technology of soybean products. The method comprises the following steps: (1) fresh soybeans are dipped for sprouting; the sprouted soybeans are blanched by boiled water, are added with weak base water by a certain ratio for grinding into thick liquid, and are added with a proper amount of reducing agent; a thick liquid-residues mixture is obtained after the thick liquid is grinded, and is implemented with ultrasonic treatment; the thick liquid is separated from the residues after the ultrasonic treatment to obtain crude soybean milk; (2) the crude soybean milk is temporarily heated with superhigh temperature, and is added with emulsifying agent for evenly mixing; the mixed soybean milk is homogenized for concentrating in vacuum, spraying and drying to obtain the instant soybean milk powder. Technique equipment needed by the method is simple, and is safely operated; and the method applies the soybean sprouting technology and the ultrasonic treatment technology, and uses the synergistic effect of adding granulesten for emulsifying, so that the prepared soybean milk powder has the advantages of high nutritional value, good digestibility and prominently improved instant property compared with the traditional technique.