The invention belongs to the technical field of radioactive source preparation, and particularly relates to a magneto hydrodynamics electro-deposition method for preparing a high-resolution alpha radioactive source. The method comprises the following steps that a permanent magnet is placed at the outside of a deposition tank, and a magnetic field is exerted on a deposition system; under the condition of the coexistence of the magnetic field and an electric field during a deposition process, Lorentz force perpendicular to the directions of the magnetic field and the electric field is generated; the presence of the Lorentz force accelerates liquid phase mass transfer in deposition liquid, and the thickness of a cathode diffusion layer is decreased; and while accelerating the deposition rate and improving the deposition efficiency, the resolution of the prepared source can be remarkably improved. According to the magneto hydrodynamics electro-deposition method for preparing the high-resolution alpha radioactive source, the problem that the energy resolution of a radioactive source prepared by a traditional electro-deposition method is low is solved, and the ordinary electro-deposition method for preparing the radioactive source is greatly improved and optimized.