The invention discloses a preparing method of a magnesium alloy material. A zinc film is plated on the surface of the magnesium alloy material, a gradient structure is formed, the production efficiency is high, and corrosion resistance and mechanical strength of the magnesium alloy are improved; according to the method, vacuum coating and the diffusion technology are combined, the pretreatment procedure is simplified, and a technology capable of finishing pretreatment and diffusion coating at a time is formed; no damage to the magnesium alloy material is caused, coating and a magnesium matrixmaterial are tightly combined, the diffusion layer is more uniform and consistent, production efficiency is improved, assembly line production is facilitated, and meanwhile, the beneficial effects ofbeing free of powder rising in the working site, green and environment-friendly are achieved; in addition, the alloy element and the rare earth element in the magnesium alloy material have a synergistic effect, the mechanical property and the specific conductance of the magnesium alloy material can be obviously improved, and the comprehensive property can be obviously improved.