The microstructure of AZ80 magnesium alloy under different conditions was observed and studied using electron backscatter diffraction (EBSD) technology, the microstructure evolution of AZ80 magnesium alloy under different conditions was analyzed. The results show that in accordance with the order of as-cast, homogenized and deformed states, the average grain size gradually decreases, the average grain shape aspect ratio showed a trend of increasing first and then decreasing, the network β-Mg17Al12 phase gradually disappeared, improved plasticity and strength of the material. The coordination of grain boundaries is mainly affected by grain boundary migration and geometrically necessary dislocations density, with the migration of grain boundaries, the low-angle grain boundaries gradually increase, which hinders the progress of recrystallization, and the recrystallization area has a tendency of increasing first and then decreasing, the substructure region gradually decreases, and the disappearance of the substructure region provided energy for the formation of twins and promoted the formation of twins. The geometrically necessary dislocations density has a trend of reducing first and then increasing, the decrease of geometrically necessary dislocations density promotes the growth of twins and the rotational movement between grains, the increase of geometrically necessary dislocations density hinders the growth of twins and the rotational movement between grains. The deformed magnesium alloy has a typical basal texture.