The invention discloses a preparation method of high-purity phytin. The method comprises the following steps: mixing taken rice bran and water at a certain ratio and stirring evenly; adding high-purity hydrochloric acid to a mixed solution of the rice bran and water, keeping the pH of the mixed solution within a certain value and extracting the mixed solution; adding an additive for removing protein, starch, ashes and saccharides to the liquid obtained through extraction and carrying out filtration and ion exchange filtration on the liquid to obtain a high-purity dilute phytic acid solution; adding high-purity calcium and magnesium oxides or high-purity calcium and magnesium hydroxides to the high-purity dilute phytic acid solution for reaction, adding a high-purity sodium carbonate water solution for pH adjustment; and carrying out filter pressing, washing and drying on the reacted solution to obtain a high-purity phytin solid. The preparation method has the beneficial effects that the prepared phytin does not contain any impurity, and high purity and high quality of a product are ensured to meet high standard quality requirements of medicines and health products.