Abstract: A joint model based on particle flow was built successfully and the mechanical properties of the fill joint were investigated in this study. The morphology of damage and the crack evolution mechanism of roughness of the jointed model were also analysed from the viewpoint of meso-mechanics. At the same time, the influence of the value of the JRC(joint roughness coefficient), fill strength, interface, and fill thickness on the mechanical behaviour have been analysed. The detailed results are as follows:(1) The normal stress has a significant influence on the peak shear stress, contact condition, and contact force of the joint. With higher stress, the bond break at the joint surface becomes apparent; (2) The joint peak shear stress increases with an increase in the JRC value, and the shear strength parameters for cohesion and friction angle exhibit linear and nonlinear increases with the increase in the JRC value, respectively; (3) The joint peak shear stress increases with the strength of filling material. However, the strength of filling material has a different influence on the cohesion and friction angle of the fill joint. Cohesion increases with an increase in material strength. The friction angle decreases as the fill strength ratio changes from 0.1 to 0.3, and increases when the fill strength ratio exceeds 0.3; (4) When the normal constant load is small, the interface has a significant influence on the peak shear stress, but when the normal constant load is large, the influence is weaker. Joint shear-strength parameters for cohesion increase with the increase in the strength of interface, but the friction angle shows the opposite trend with cohesion; (5) With increasing fill thickness, the mechanical parameters of the joint model exhibit an obvious downward trend. However, with a further increase in thickness, the decrement in the mechanical parameters is less pronounced.