Abstract: Liaojiaping dangerous rockmass is located on the left bank of the Changjiang River,with fractures developed,it threats the local residents and Changjiang sea-route badly.There are seven soft layers and two groups of fractures in the rockmass,the deformation mechanism is the "secondary toppling" mode.Using UDEC model,the paper make numerical analysis on the toppling mechanism of the rockmass.The simulation results show that the crack failure by secondary toppling is reduced from the face to the back.Toppling block is controlled by the soft layer,as a whole,the block doesn’t cross the soft layers,so it is impossible to topple as one-piece.When dangerous rockmass or rock piles are formed in secondary cliffs,there are two failure type toppling to the front and toppling to the back.The toppling direction is related with belowed soft layer’s failure seriously,when the toes of soft layer failure seriously the rockmass topples to the front,or the heel of soft layer failure seriously the rockmass topples to the back.The results of numerical analysis offer scientific idea for controlling of deforming rockmass,also it has important instruction to other dangerous rockmasses study in the Three Gorges Reservoir Region.