Abstract：As one of typical two geologic disasters in the Three Gorges Reservoir，unstable rock is the result from disorder interaction of multi-factors such as geologic strata，geomorphologic characteristics，fissure water pressure and earthquake，etc. On the basis of failure mode，the unstable rock is divided into three models，i. e. unstable sliding rock，unstable fall rock and unstable topple rock. The main loads to cause unstable rock failing in the reservoir are weight of unstable rock，fissure water pressure in nature，fissure water pressure in strong precipitation and earthquake force. There are three types of load combination. The first one is weight and fissure water pressure in nature，the second one is weight and fissure water pressure in strong precipitation，and the third one is the first type of load plus earthquake force. According to both unstable rock model and load combination the stability calculation method is developed through limit equilibrium theoty and rock mass structure theory. These proposal methods have been extensively applied to the stability analyses and control of unstable rock in the Three Gorges Reservoir.
