In the paper, process of AZ31magnesium alloy strip by strip casting has been studied. The microstructure of AZ31 magnesium alloy strip has been analyzed. The result show that technology of strip casting can eliminate segregation and refine grain. Also, microstructure's formation mechanism has been studied. In addition, the maximal reduction arrived 50% when magnesium alloy has been hot rolled at 240~300℃.