The invention provides formula powder for phenylketonuria children and a preparation method thereof. The formula powder comprises solid glucose syrup, amino acid, fatty acid, nucleotide, fish oil, dietary fiber, composite vitamins, composite mineral substances and an emulsifier, and is prepared by using a wet-method preparation process of materials. According to the formula powder, special free amino acid is adopted, a proper amount of free L-tyrosine is screened and optimized, and phenylalanine is removed, so that the physiological needs of sick children are met, and at the same time hypersensitivity of phenylketonuria infants is effectively prevented; in the formula, the components have the mutual synergistic effect, the powder is approximate to breast milk in absorption, taste and the like, children can absorb sufficient nutrition after taking the powder, and meanwhile anaphylaxis such as diarrhea can be effectively reduced; and the formula powder is simple in preparation method and applicable to requirements of large-scale industrial production.