Abstract: The twin structure of AZ31 magnesium alloy commercial sheet was introduced by pre-rolling along the TD direction. The effect of twin orientation on the anisotropy of magnesium alloy sheet was investigated by tensile test. The results show that the commercial AZ31 sheet has a strong basal texture and small plane anisotropy.Side-rolling along the TD direction can introduce a large number of tensile twins, and produces twin orientation with c-axis//TD. A single c-axis // TD texture is formed in the AZ31 plate after strain 8% and annealing. The generation of twin orientation greatly reduces the tensile yield strength in the TD direction and the 45° direction, which in turn leads to strong in-plane anisotropy. In addition, the formation of the c-axis//TD texture will enhance the deformability in thickness direction, thereby greatly reducing the plastic strain ratio of the sheet.