Rock masses consist essentially of intact rock and discontinuities such as joints. Blasting is mostly used method for the rock excavation. To investigate the effects of joints on the fragmentation by blasting, three models with different joint patterns and one model without joint were created in the LS-DYNA code. In these models, a bonded particle model was used to represent the rock to be blasted, a finite element model was adopted to model the remaining rock mass and a particle blast model was employed to describe the detonation of explosives. To validate the contact model for joints, the fragmentation pattern and the individual particle motion from two single borehole shot models with and without joints were compared. The numerical results indicated that the existence of joints has a significant effect on fragmentation and vibration. The models with joints produced finer fragmentation compared to the model without joints in the paper.