Abstract: Anhui Shitai Pumped Storage Power Station is located at the northeastern margin of the Jiangnan Old Land, with a complex regional geological structure background and has experienced multi-stage tectonic-magmatic evolution. During the engineering investigation and construction of the lower reservoir, a series of special geological phenomena were revealed, mainly including the development of superimposed folds and complex rock mass fracture zones formed by magmatic intrusion and alteration. Based on the theory of regional geotectonic evolution and the principles of engineering geology, combined with field geological survey and borehole exposure data, this paper deeply analyzes the genetic mechanisms of the above special geological phenomena in the lower reservoir. The research shows that the multi-stage Mesozoic activities of the Jiangnan Fault Zone and lithospheric extension are the fundamental dynamic background leading to rock mass fragmentation and dense joint development in this area; while lithological differences and the long-term deep circulation of groundwater along tectonic weak zones jointly induce the formation of altered fracture zones. Aiming at the adverse effects of such special geological phenomena on the stability of the inlet and outlet slopes of the lower reservoir, this paper puts forward targeted engineering treatment recommendations and optimized support measures, aiming to provide reliable geological scientific basis for the safe construction and long-term stable operation of the power station.