Dislocation mechanism operating in dynamic recrystallization （DRX） during hot compression of Mg-5.51Zn-0.49Zr alloy was investigated by X-ray diffraction, optical microscopy and transmission electron microscopy. The results showed that the continuous DRX occurred at a low strain rate of 1×10^-3s^-1, which was associated with the operation of the single gliding dislocation climbing. At the intermediate strain rate of 1×10^-2s^-1, the continuous DRX was associated with the climbing of the gliding dislocation array as deformed at an elevated temperature of 350 ℃, and in contrast, the discontinuous DRX was observed and associated with the bulging of subgrain boundaries as the deformation temperature was raised to 400 ℃. The continuous DRX was associated with the climbing of the leading dislocation ahead of pile-ups, and resultant rearrangement of misorientated flat dislocation pile-ups as the strain rate was increased to 1×100s^-1. It is suggested that the mechanism predominating the dislocation climbing was changed from the vacancy migration to the stress acting on the leading dislocation ahead of the pile-up as the strain rate was gradually increased.
