The invention discloses a magnesium alloy anticorrosion coating and a preparation method thereof, and belongs to the field of metal corrosion and protection. The invention aims to solve the problem that magnesium alloy is easy to corrode in application. A dry film of the coating provided by the invention comprises the components in percentage by mass: 19 to 25 percent of epoxy resin, 19 to 25 percent of polyamide, 50 to 60 percent of pure magnesium powder, 0.5 percent of deformer BYK-A530 and 0.5 to 1.5 percent of titanate coupling agent. In the method, the epoxy resin and the polyamide are respectively dissolved in the mixture solution of xylene and n-butanol in a mass ratio of 7:3 to respectively prepare the solution with the mass fraction of 62.5 percent; the magnesium powder and epoxyresin solution are mixed uniformly, the titanate coupling agent is added, the mixture is stirred uniformly, polyamide solution and the deformer BYK-A530 are added, and the mixture is dispersed for 5 minutes and cured for 5 minutes to obtain the magnesium alloy anticorrosion coating. The coating has the advantages of high cathodic protection and corrosion resistance and simple preparation process.