Molecular dynamics simulation is applied to investigate the microstructure evolution of magnesium single crystals under c-axis extension at different temperatures. At low temperatures, both {10 ˉ 12} and {10 ˉ 11} twins are observed. At elevated temperatures, {10 ˉ 11} twining decreases quickly with increasing temperature, while the amount of {10 ˉ 12} twins increases. The {10 ˉ 12} twin is found to be the main deformation mechanism under the c-axis tension in the magnesium single crystal. Meanwhile, shear bands are also observed during deformation. When the temperature is beyond 500 K, the non-basal plane slip due to the thermal activation is found. The stress-strain curves related with deformation behavior at atomistic scale are presented. At low temperatures, both {10 ˉ 12} and {10 ˉ 11} twins are observed. At elevated temperatures, {10 ˉ 11} twining decreases quickly with increasing temperature, while the amount of {10 ˉ 12} twins increases. The {10 ˉ 12} tw is found to be the main deformation mechanism under the c-axis tension in the magnesium single crystal. Meanwhile, When the temperature is beyond 500 K, the non-basal plane slip due to the thermal activation is found. The stress-strain curves related with deformation behavior at atomistic scale are presented.