Orientation mapping based on EBSD technique was applied to analyze the rules of orientation evolution of grains in AZ31 magnesium alloy. Results show that not only under deformation strain rate Of 1 X 10(-2)s(-1), but under 4 x 10(4) s(-1)(the superplastic deformation condition), grains in all samples with initial textures rotate gradually to near basal orientation ({0002} parallel to compression plane) at different ways, and basal texture becomes stronger with increasing strain, which indicates plastic slip plays an important role during hot deformation. Otherwise, no evident non-basal pyramidal slip of < a+c > as some studies mentioned was observed in the sample with the initial basal texture, and the basal orientation is kept unchanged during the deformation process, which suggests that basal slip is the uppermost plastic slip mechanism in this sample. In addition, the phenomenon of viscous laminar flow was observed in the sample with initial basal texture.