Slope failure disasters have been increasing in recent years, and although research on heavy rains and earthquakes that cause them is progressing, it is difficult to investigate the deformation mechanism inside slope that is the predisposing factor. Therefore, in order to deal with slope disasters, it is a agenda to evaluate complicated gravitational deformation mechanism inside the slope.Firstly, We confirmed that the balanced cross-section method can evaluate gravitational deformation mechanism inside a dangerous slope. Secondly, we developed a new finite element method （BaFEM） as a numerical analysis method that can reproduce the balanced cross-section method quickly and universally. In the balanced cross-section method, large deformation accompanied by displacement and separation of strata occurs. For this reason, it is difficult to replicate the balanced cross-section method with the previous finite element method. Therefore, we improved the previous finite element method and proposed a new method of creating and deleting contact elements repeatedly by separating the elements from a certain distance. And, complex gravitational deformed slope such as buckling and toppling, which cause slippage and separation, can be replicated, and the stress and share strain inside the slope during large deformation can be evaluated moment by moment.As a result, it is possible to predict not only the deformation mechanism but also the future deformation in the reproduction analysis of the actual gravitational deformation slope using BaFEM.