The underground powerhouse of a hydropower station lies in stiff and integrate granite expensive some fault. A lot of monitor instruments are installed during construction

and much information are received from that. Based on the complete observation information of the pumped-storage station

the deformation data of the wall rock are studied. And then the conclusion is the underground power-house are steady in principle. At the same time，the numerical model of underground house is analyzed by using finite difference method. The changing law of displacements and stresses of rock-mass is studied and the dynamic changing process is forecasted truly. The displacements from computing and observing of some points in the rock are contrasted. All of those can offer the reference to other stability analyses of large underground power-houses.