This invention is a high-intensive heat-fast magnesium alloy and its preparation method, and the magnesium alloy has the following components with their weight percentages: 6-15%Gd, 1-6%Y, 0.35-0.8%Zr, 0-1.5%Ca, and impurity elements Si, Fe, Cu and Ni with their gross less than 0.02%, and the rest percentage is Mg. while melting, add Gd, Y, Zr in the Mg melt in Mg-Gd, Mg-Y, Mg-Zr forms, then carry out solution treatment to the magnesium alloy under 450-500deg.C for 6-12 hours, squeeze in in 350-450deg.C, treat in time the squeezing stick for 10-16 hours in 225deg.C to improve its strength.