Magnesium alloys are materials with predominant performance, but its formability is needed to be improved. Increasing the content of soluble inside grain, the formability will be improved. The results show that when magnetostatic field is applied to the process of solidification of magnesium alloy, the grain is refined, and the soluble content inside grain increases, on the contrary the content of soluble decreases at grain boundary. Compared with the common solidification, when the magnesium alloy ZK60 is solidified under magnetostatic field, the content of calcium and zinc decrease respectively from 15. 62%, 5. 6% to 14. 85%, 3.7% at grain boundary; the content of zinc increases from 0.68% to 0.91% inside grain. This will increase distortion inside matrix and more dislocation will supply slid deformation, as a result the formability will be improved.