An asymmetrical rolling of AZ31 alloy sheets was carried out at 473 K with a high reduction ratio of 70% in thickness prior to tensile-tests. For the as-rolled sheet, tensile tests were performed in a temperature range of 473 ~ 673 K at a constant strain rate of 1 × 10-3 s-1. Tensile elongation increases with increasing reduction ratio in the as-rolled sheets. A large elongation of above 530% was obtained in the specimen deformed at 673 K for the sheet fabricated by 70% thickness reduction. Although the extent of grain growth was remarkable in a high temperature range, the tensile elongation increases with increasing the tensile temperature.