The invention relates to an auxiliary rice flour for infants and a preparation method of the auxiliary rice flour. The auxiliary rice flour is mainly formed by refining rice flour ground with water, whole milk powder, white granulated sugar, cream, calcium lactate, zinc gluconate, ferrous gluconate, fructo-oligose, soyabean lecithin, beta-carotene, niacin, docosahexaenoic acid, arachidonic acid, vitamin A, vitamin D3, vitamin B1, superfine lily powder, superfine radix polygonati officinalis powder, superfine Chinese date powder and superfine tremella powder. The auxiliary rice flour is prepared through the steps of superfine grinding, pelleting, microwave sterilizing and the like. The preparation method is simple and feasible, the auxiliary rice flour is suitable for large-scale industrial production, a new formula is adopted, lily, radix polygonati officinalis, Chinese dates and tremella are added and ground superfinely, and effective constituents can be directly absorbed, and the functions of adjusting immunity and improving constipation are achieved; the adopted production technology remains nutritional ingredients of food, the loss is reduced, the solubility is high, energy is saved, and consumption is reduced; the microwave sterilization manner is adopted, so that various microorganisms comprising bacillus can be killed thoroughly, and the product quality safety is guaranteed.