Taking an asphalt concrete face rockfill dam (CFRD) on the 100 m-level deep soft overburden of the upper reservoir of a pumped storage power station as an example, the deepest overburden section of the dam is selected, and the stress and deformation behavior of the dam body during the filling period and the water storage operation period are calculated and analyzed by Biot’s consolidation theory, with emphasis on the distribution law of consolidation deformation of the dam foundation and the dissipation of excess pore water pressure. Meanwhile, for the dam foundation with saturated soft clay overburden, the total stress method of “ φ =0” is used to analyze the deep anti-sliding stability of the dam foundation during construction. The results show that during the dam filling process, the excess pore water pressure in the overburden keeps increasing, diffusing and dissipating simultaneously. The complicated changing process is closely related to the permeability of the stratum. When the dam body is filled to about 1/3 of the dam height, the excess pore water pressure in the overburden reaches its peak. The relatively large permeability of the upper gravel clay overburden makes most of the excess pore water pressure in the overburden dissipate when the dam construction is completed, and the overburden is basically consolidated five years after the construction. Due to the rapid dissipation of pore pressure in the gravel clay overburden during dam filling and after dam impoundment, and the additional stress of deep saturated clay is small, the settlement increment after dam construction is only -7.35 cm (excluding rheology), accounting for about 2.18% of the final stable settlement of -337.58 cm. The safety factors of anti-sliding stability of dam slope and deep overburden calculated by total stress method, and effective stress method with corresponding parameters under the conditions of completion period, storage period and reservoir water level change are all greater than the corresponding allowable values according to specified design codes, thus the possibility of dam slope instability is small.