Abstract: The plastic failure pattern of soil and the reasonable kinematic pattern satisfying the boundaryconditions are assumed for the pile anchorage system in the foundationpit in this paper, unlike the conventional method, where soil is divided intoseveral rigid pieces. The safety factor for thevertical slope of the pile anchorage system in the foundation pit under attachedload is calculated based on the upper bound method of limit analysis ofsoil plasticity. An engineering example is given to validate themethod with software FLAC.