High temperature deformation and crystallographic orientation distribution of the Al-Mg-Mn sheet worked by the continuous cyclic bending (CCB) and the subsequent annealing have been investigated. The sheet consists of a coarse-grained surface and fine-grained center layers. The elongation to failure has a peak value at 713K at initial strain rates of 5.6 x 10(4) s(-1) and 5.6 x 10(-3 s-1) in both of as-received sample (0P) with fine grains and CCBent and annealed one (20P_A) with the coarse and the fine grains in spite of different microstructures. The m value decreases for 20P_A and increases for 0P with increasing temperature. However, the increase of the m value is not correspondent to the change in the elongation. The deformation mechanism is discussed with relation to activation energy. The SEM micrographs of the original surfaces of tensile specimens deformed to failure reveal that at the relatively high temperatures many cracks are formed inside the coarse grains. The change in crystallographic orientation distribution is investigated during tensile testing in consideration of the deformation mechanism.