Abstract: It is very important to investigate the forces acting on the rock mass by the seepage flow in fracture network. The forces acting on the fissure walls by the seepage flow include the hydrostatic seepage pressure and the hauling force. Based on the cubic law of the single fissure flow, the equation of the hauling force with which the single fissure flow acts on the fissure walls is deduced by means of the momentum law of fluid mechanics. The equation is compared with the hydrodynamic pressure theory of continuum seepage. The result in the paper is a foundation for couple mechanism analysis of flow and stress in fractured rock mass.