Abstract: In order to study the influences of the drag force of slide fissure flow on the stability of the horizontal-push landslide, a seepage-runoff coupled model of horizontal-push landslide is established. The Navier-Stokes equation is used to describe slip surface runoff, and the Brinkman-extended Darcy equation to describe the seepage of porous media in weak layers. The fluid flow in the runoff and seepage areas all satisfy the continuity equation, and the fluid at the interface satisfies the condition of equal flow velocity and continuous shear stress. According to the above conditions, the distribution of flow velocity in runoff and seepage areas is deduced, and Newton's internal friction law is introduced to obtain the drag force on the sliding surface. Based on the rigid body limit equilibrium theory, the stability of run-flat slopes under runoff condition is analyzed, and the relation between the corrected safety factor of anti-slide stability and the critical depth of trailing edge fissures is obtained. Combined with the engineering examples, the influences of the water depth at the trailing edge, dip of the slip surface and width of the slip surface crack on the safety factor are discussed. The results show that the safety factor of landslide decreases by 5.90% when considering the drag effect of bottom fissure fluid. Therefore, in the analysis and calculation of the stability of the horizontal-push landslide, the drag force of the fissured water flow in the sliding surface should be considered.