The invention discloses a preparation method of a high-purity superfine aluminum oxide powder body. The method takes the characteristic of using aluminum oxide as amphoteric oxide, and prepares the high-purity superfine aluminum oxide powder body through alkali dissolution, electrolysis, acid dissolution, crystallization, microwave pyrolysis, and high-temperature pyrolysis; the preparation methodsolves the technical problems that the existing preparation method of the high-purity aluminum oxide powder body is high in production cost and complex in technique and the acquired high-purity aluminum oxide powder body is required to perform secondary grinding. The method is simple in technique and low in cost; the method can be applied to prepare the high-purity superfine aluminum oxide powderbody.