Misfit dislocation structures at twist-grain boundary and its effect on grain boundary strength are investigated by using molecular dynamics simulation with EAM potential. The results reveal that the density of misfit dislocations which are formed on small angle twist-grain boundary is increased as the twist angle increased. Dislocations nucleate at each unit of the dislocation networks and the yield stress is increased as the density of misfit dislocations increases since grain boundary is strengthened by the interaction between dislocation networks. Face defect is formed at large angle twist-grain boundary, and the dislocations nucleate at the atomically sharp corner of the grain boundary. The yield stress is kept almost at the same value since there is little effect on the nucleation force of dislocation on face-defect grain boundary.