As one of dominant geologic disasters in the area of the Three Gorges Reservoir of China, perilous rock displays some features such as much quantity, extensive distribution, bad stability and strong fatalness. The internal reasons is that the stratum composed of soft rock and inflexible rock, steep slope and obvious unloading, while both fissure pressure in control fissure of perilous rock and earthquake force are external reasons for perilous rock to develop. In present paper, the authors establish chained mechanism in views of Geomorphology, and divide the evolution of perilous rock into eight stages. Further, avalanche of perilous rock is divided into three stages, 1) the free falling stage, 2) the initial bounce stage, and 3) the later bounce stage. Methods to calculate moving routine after avalanching of perilous rock are established based on kinematics.