Today, grouting is used as an aid in ground improvement in most civil and mining projects. Groutability and grout penetration depth are subjects that are considered in grouting operation. As discontinuities compose the main paths for fluid flow in jointed rock mass, geometric characteristics, such as joint aperture, spacing and orientation, affect the grout flow. On the other hand, fluid flow in joint is a hydromechanical process and the state of applied stress on joint affects the fluid flow. Knowledge of these parameters has advantages in prediction of grouting results (grout penetration and intake). Unlike water (Newtonian fluid), stable cement-based grout usually acts as a Bingham fluid. In this study the effect of important joint geometric characteristics on grout intake and penetration depth was simulated hydromechanically using the UDEC code. The gained results show that grout intake and penetration depth increase as joint aperture and normal stiffness increase and in-situ stress decreases. Increase in joint spacing does not have any effect on penetration depth but decreases the grout intake. The effect of joint orientation on grouting process is strongly dependent on in-situ stress state.