The lower reservoir of the Fengning Pumped Storage Power Station was upgraded based on the original reservoir of the Fengning Hydropower Station. Following upgrading and heightening, significant upgrades were made to the operational level, flood criteria, grade of hydraulic structure, as well as the seismic precautionary criterion of the reservoir, surpassing the parameters of the original design. The dam adopts a upgrading and heightening plan of filling with stone materials downstream of the original dam. This study explores the adaptability of the original dam body and its seepage control system to the dam’s upgrading and heightening, and also presents a comprehensive study of the design scheme for the dam’s upgrading and heightening. The findings offer a reference framework for the reconstruction and upgrading of similar pumped storage facilities.