The invention provides an aluminum-free high-strength heat-resistant die-casting magnesium alloy. The alloy comprises the following chemical compositions in percentage by weight: 7.5 to 12.5 percent of Gd, 2.5 to 3.5 percent of Y, 0.3 to 1 percent of Zr, 0.5 to 1.5 percent of Zn, less than or equal to 0.02 percent of Si, less than or equal to 0.003 percent of Fe, less than or equal to 0.003 percent of Ni, less than or equal to 0.003 percent of Cu, and the balance of Mg, wherein Si, Fe, Ni and Cu are impurity elements. By adding Gd, Y, Zr and Zn as rare earth elements to magnesium melt, the invention develops the magnesium alloy which is high in strength, high in heat resistance and suitable for die casting. Although the prices of the magnesium alloy is 2 to 3 times that of the common die-casting magnesium alloy, the magnesium alloy has the advantages of good die-casting forming performance, high mechanical properties and good heat resistance, can be used for parts requiring high heat resistance, and has great potential for development.