The perilous rock is one of the typical disasters in the Three Gorges reservoir region; it can be classified as two types in views of perilous mode

i.e. falling perilous rock and toppling perilous rock. Crack propagation of control joint of perilous rock under loads is the key process in failure of perilous rock. In this paper taking the control joint in perilous rock as one crevice in a sample

to solve the moving discontinuities of joint propagation by extended element method and explore the crack propagation behavior of control joint of perilous rock under loads. The Taibaiyan cliff at Wanzhou is a representative case of massive perilous rocks in the area. Using this cliff as an example

the effect of joint location

obliquity and rock tensile strength on the failure mode and magnitude of safety factor were investigated. The results demonstrate that with the decreases of rock tensile strength

the perilous rock stability decreases; and with the decreases of control joint obliquity

the perilous rock stability increases. The destructive mechanism of two unstable modes for perilous rock is tension-shear. As opposed to toppling perilous rock

under the same conditions

the stability of falling perilous rock is even worse.