The invention discloses a high-strength plastic magnesium alloy material low in rare earth content. The high-strength plastic magnesium alloy material low in rare earth content comprises, by mass percentage, 7.42-8.55% of aluminum, 1.57-2.23% of tin, 0.90-1.38% of zinc, 0.42-1.53% of yttrium and the balance magnesium. Multiple types of second phases, uniform and fine microscopic structures and weak base surface structures are uniformly distributed in alloy, so that the alloy is high in strength and plasticity. The invention further discloses a preparation method of the high-strength plastic magnesium alloy material low in rare earth content. The nanometer-scale and micron-scale second phases and grains which are relatively small in size are uniformly distributed in the structure of the prepared magnesium alloy, and mechanical performance of the magnesium alloy is remarkably improved.