Abstract: End constraint has an influence on distribution of stress in rock specimen, failure pattern and pattern of shear zone. FLAC-3D is adopted to simulate the influence of end constraint on patterns of shear bands, velocity and displacement fields. For a stiffer constraint, a conjugate shear zone occured in central part of the specimen; Otherwise, an inclined shear zone initiated on the end of the specimen. The inclination angle of shear zone becomes steeper with increasing rigidity of platen. Four small blocks have properties of integral movement. The displacement gradient along the margin shear zone is larger. It shows that the blocks slide alone shear zone is of shear failure nature. The result of numerical simulation is consistent with some experimental results.