Abstract The influence of the rolling speed on microstructure and mechanical properties of as-rolled AZ31 Mg alloys sheet was critically examined. Samples were hot rolled by nearly 55% thickness reduction in a single rolling pass at rolling speeds varying between 3.5 and 12.1m/min. The results showed that twinning dominated the deformation at lower rolling speed and dynamic recrystallization was constricted in shear bands. While, at high rolling speed, dynamic recrystallization behavior was largely extended and microstructure became homogeneous. The yield behavior of as-rolled sheets was affected by the recrystallized grains formed during rolling. The tensile ductility was gradually improved as rolling speed increased, due to the enhancement of dynamic recrystallization. The dynamic recrystallization is an effective way to consume the deformation energy, which may suppress edge crack initiation.