The invention discloses a method for preparing hafnium carbonate in the field of hydrometallurgy. Hafnium carbonate powder is prepared through a two-step method of: (1) preparing basic hafnium sulfate by hydrolysis: dissolving hafnium oxydichloride in deionized water to obtain the solution of the hafnium oxydichloride, adding a certain amount of sulfuric acid and ammonia water into the solution for thermal insulation hydrolysis for 8 hours in water bath; and (2) transforming the basic hafnium sulfate into the hafnium carbonate: dissolving a certain amount of carbonate in the deionized water to obtain solution of the carbonate, mixing the basic hafnium sulfate prepared in the last step and the solution of the carbonate uniformly for a thermal insulation reaction for 2 hours in water bath. By adjusting the molar ratio of transforming agents, namely SO42- and Hf4+, the method can ensure that the hydrolytic precipitation in the first step is more complete, the concentration of the Hf4+ in hydrolysis mother liquor is quite low, and the recovery rate of metal is high; and by using different carbonate transforming agents, the method can prepare the hafnium carbonates with different carbon contents, and the hafnium carbonates have different solubilities in citric acid, but all have good dissolubility in acetic acid.