Abstract: Based on the characteristics of seepage in fracture network of rock mass, two forces the normal seepage pressure and the tangent force applied to the fracture walls are studied. The equivalent node forces of joint element are deduced under the two dimensional and three dimensional conditions. An example shows the effect of seepage in fracture network on the stress of rock mass. It comes to the conclusions that seepage forces in fracture network of rock mass decrease the compressive stress of rock mass above the fractures and increase the compressive stress of rock mass below the fractures (10.53%). The forces increase the tensile stress of rock mass (9.09%), and increase the shear stress of rock mass (23.75%).