The invention provides an anti-corrosive paint used for a magnesium alloy and a preparation method thereof. The dope counted according to the weight portions contains matrix resins, paints, addition agents, fittings and an organic solvent; wherein, the fittings are inorganic fittings which contain or do not contain matt powder; the matrix resins consist of saturated polyester resins, amine resins and epoxide resins with a weight ratio of 35 to 40: 7 to 9 : 3 to 6. The preparation method thereof includes the steps of mixing and grinding the components. The dope provided by the invention has the advantages of high anti-corrosive capacity as well as good adhesive attraction with the magnesium alloy and the coatings on the upper layer thereof.