The flow stress of AZ41M (Mg-Al-Zn-Mn-Ca) and ZK 60 (Mg-Zn-Zr) wrought magnesium alloys under the deformation conditions of twin rolling casting and hot compression at different temperature and strain rates was studied. Deformation behavior and failure mechanism of them were discussed. Microstructure evolutions were analyzed by optical microstructure and electron backscatter diffraction technique. The results have indicated that AZ41M and ZK 60 have different strain-stress curve under the same conditions. Working hardening results in occurrence of cracks in or around the shear bands. The recrystallized, equiaxed, and fined grains in shear bands attribute to recovery and recrystallization, grains refinement causes local working hardening as well as decreases of crack tip driving forces. Stress concentrated in shear bands causes crack initiation and propagation. Nucleus of cracks due to casting defects is another failure mode. With the increase of strain, dislocation rearranged in subgrain level while the low angle grain boundaries continuously evolved into high angle grain boundaries.