In this paper, an anchorage scheme against the imminent failure of slope in practice has been proposed by considering on-site monitoring data and 3D numerical modeling. From the results, the position, time interval and initial time of internal shear slip plane are observed, according to the continuous monitoring data of the slope. Therefore, the position and shape of a potential slide plane can be predicted. Since the influence of the section morphology on slope stability and deformation is considered in this study, the results obtained by 3D numerical modeling are more reasonable. By fitting the external deformation and sliding surface with the numerical modeling and the measured data, the equivalent mechanical parameters of slope in any state are determined, according to the limit equilibrium condition of the imminent failure slope. From the equivalent mechanical parameters, the ultimate shape and position of the potential sliding surface are obtained by 3D simulation. The length and density of the reinforcement anchor cable can be further decided properly. The performance of this case study demonstrates that the proposed reinforcement scheme is reliable.