Abstract：Tiger Leaping Gorge hydropower station is a large project to be build on Jinsha River in southwest China. Longpan is one of the comparative dam addresses，but large-scale deviant rock mass was discovered on the right bank slope，where an old landslide once happened，so that Longpan dam was given up. In the latest studies，based on systematic field survey，especially through CSAMT exploration and comprehensive analyses of deformation characters of the rocks，it was proven not to be an old landslide but a deforming slope. The geologic structure of Longpan slope is very specific，and the dip direction of the stratums is opposite to slope. The sandstone stratums and slate stratums intercross alternately，and deep-seated stratums are dominate sandstone rock which are thick and hard，with large inclination angle. But the top of the slope stratums are with thin and small inclination，and the hard and soft rock-formations intercross mutually. Lake sediments at the foot of the slope account for the particular geologic structures. The results show the geomechanical deformation patterns are as follows：(1) the activities of the fractures induce deeply fragmentized phenomenon；(2) lithosphere raising，valley cutting downwards and transforming of the regional tectonic stress-field cause unloading rebound and cracking of lower rock mass；and (3) the main deformation pattern of top stratum was bend-creeping. By reason of the compressibility and plastic flowing of lake sediment and superficial stratum at the foot of the slope，rock mass is adjusting to the structure by the way of stagger-sliding and lateral expanding locally，but there is no weak zone of penetrating the slope. The mode can be named Longpan-pattern，which is universal in Tiger Leaping Gorge Reach in Jinsha River，and it is significant to choose the dam address and analyze the stability of reservoir banks.
