The invention belongs to the technical field of dissolution and purification treatment technologies for ammonium biuranate in the uranium purification and conversion process, in particular to the technologies of dissolution of the ammonium biuranate, extraction and purification treatment of a uranyl nitrate solution and the like and provides a uranium purification method for the ammonium biuranate. The uranium purification method for the ammonium biuranate comprises the following steps that (1) dissolution is conducted so as to prepare a qualified uranyl nitrate solution for extraction and purification; (2) extraction is conducted, the solution to be extracted and an extraction agent are mixed and conduct matter transfer in a pulse extraction column, uranium in the material is carried into the extraction agent, and an organic phase containing the uranium is obtained; (3) washing is conducted, the organic phase containing the uranium and a washing agent are fully mixed and conduct matter transfer in a pulse washing column, impurity elements in the organic phase containing the uranium are rewashed and enter a water phase, the purity of the uranium is further improved, and the purified organic phase containing the uranium is obtained; and (4) reverse extraction is conducted, the purified organic phase containing the uranium and the washing agent are fully mixed and conduct matter transfer in the pulse washing column, the uranium enters the water phase again through reverse extraction, the purified uranyl nitrate solution is obtained, and an uranium oxide is prepared from the purified uranyl nitrate solution through concentration and denitration manners.