Magnesium alloy has a hexagonal close-packed crystal structure, and its plasticity is poor at room temperature. This is primarily due to the small number of movable slip systems at room temperature, which is prone to deformation texture. Therefore, temperature and compression deformation play an important role in the regulation of plastic deformation. In this work, AZ80 magnesium alloy was subjected to multi-pass compression deformation at a constant temperature and step-down temperature. The microstructure of the AZ80 magnesium alloy with different deformation degrees and deformation paths was observed and analyzed using EBSD. In addition, the grain boundary, dislocation density, Schmid factor, and polar figure evolution of the AZ80 magnesium alloy during hot compression deformation were primarily studied. Results show that the comprehensive effect of grain size, twinning, and texture on the plastic regulation of AZ80 magnesium alloy is better than that of single dynamic recrystallization. Moreover, three-time constant-temperature deformation (ε = 0.6) promotes dynamic recrystallization, whereas three-time step-cooling deformation (ε = 0.6) promotes plastic deformation. More 86°{10\overline{\mathrm{1}}2} <1\overline{\mathrm{2}}10> tensile twins are produced by reduced grain orientation difference, increased number of low-angle grain boundaries, and increased geometrically necessary dislocation density, which are important factors affecting the plastic regulation of three-time step-cooling deformation (ε = 0.6).