An experimental investigation was performed into the formability of magnesium alloy sheets that were hot-rolled after a semi-solid roll strip casting process. Semi-solid forming helps reduce the total product weight if the semi-solid material produced by light metals, such as aluminum and magnesium can be used to replace conventional iron and steel products. However, the problems of utilizing magnesium alloys are still related to high manufacturing costs. This means that improved quality must be balanced by economic validity. Magnesium alloy AZ31B was used in this experiment to ascertain the effectiveness of semi-solid roll strip casting for producing magnesium alloy sheets. The temperature of the molten magnesium, and the roll speeds of the upper and lower rolls, (which could be changed independently), were varied to find an appropriate manufacturing condition. Rolling conditions and heat treatment were changed to examine which condition would be appropriate for producing wrought magnesium alloys with good formability. Microscopic observation of the crystals of the finished products was performed. It has been found that a limiting drawing ratio of 2.4 was possible in a deep drawing process of the cast magnesium alloy sheets.