The effect of grain-boundary character on dynamic recrystallization was studied by means of hot-tensile tests and metallographic observations. For this purpose, Cu-Si alloy bicrystals having several [001] twist boundaries were hot-deformed at a temperature of 1023 K and a strain rate of 4.17×10⁻⁴s⁻¹, followed by H₂ gas quenching. As misorientation angle (grain-boundary energy) increases, dynamic recrystallization took place easier at grain boundary. This grain-boundary dependent characteristic of dynamic recrystallization was closely attributable to the difference in the occurrence of grain-boundary sliding, grain-boundary serration and piling up of dislocations to grain boundary followed by the development of inhomogeneous dislocation substructure nearby grain boundary. Accompanying these results, a new model of dynamic recrystallization, in which dynamic nuclei can be formed by bulging out of part serrated grain-boundary, is proposed.