Magnesium alloy is used in many different fields, but it is most common in the marine, and aerospace fields. The alloy is not used very much, though, because its mechanical properties are not good enough because of its coarse grain structure. The primary technique utilized to enhance the strength and hardness of a metal whereas maintaining its ideal ductility is cryo-rolling. This study seeks to investigate the utilization of cryo-rolling and annealing techniques to improve the mechanical and microstructural properties of the AZ31B alloy. During the experiment, cryo-rolling was done in two separate passes: 10 and 15 passes. Vickers hardness testers and tensile tests were used to test the AZ31B alloy after it had been cryo-rolled and annealed. The cryo-rolled sample was 28% harder than the basic material. After 15 passes, the cryo-rolled materials had a finer and more uniform grain structure. Cryo-rolling and then annealing the AZ31B alloy made it more flexible in terms of its mechanical properties.