The invention discloses a material for surface composite modification of magnesium alloy. The material comprises the following compositions in percentage by mass: 30 to 50 percent of glass dust (with the melting point between 350 and 500 DEG C), 10 to 15 percent of metal powder, 0.4 to 0.6 percent of defoaming agent, 2.0 to 4.0 percent of caking agent, and the balance of water, wherein the glass dust is one of borate glass, phosphate glass and lead-zinc glass; the metal powder is at least one of aluminum powder and zinc powder; the defoaming agent is one of polydimethylsiloxane, polyoxyethylene polyoxypropylene ether and polyoxypropylene glycerol ether; and the caking agent is one of polyvinyl alcohol and sodium carboxymethyl cellulose. The prepared material is coated on a foamy surface to form an alloying layer and a ceramic layer synchronously during magnesium alloy casting; moreover, the compositions of the surface layer of a cast product is in ladderlike distribution from the outside to the inside to form a composite layer, thereby providing double protection for a matrix and increasing the corrosion resistance and abrasion resistance of the magnesium alloy. The material has the advantages of low cost, simple operation, easily controlled parameters, and the like.