The present invention relates to crystalline forms of mesaconine. Specifically, the present invention relates to crystalline form A, crystalline form B and crystalline form C of mesaconine and preparation methods thereof. In the method, the mesaconine is crystallized in solvent, and then the crude crystal is dried to obtain target crystalline form. The crystalline forms of mesaconine according to the present invention have good solubility, good stability, low hygroscopicity, long-term storage capability and good reproducibility, and have a good prospect to be developed as pharmaceuticals.