Abstract: An ultra-high voltage substation is located in the mountainous area of Zhejiang Province, with a fluctuating terrain that requires half excavation and half filling. A 15m high fill slope and a 13m high excavation slope are formed. The 15m high fill slope adopts a natural sloping+retaining wall+pile scheme. By conducting stability calculations and finite element analysis, the safety of high slopes can be verified from all aspects and meet the requirements of the specifications. This article provides theoretical support and guidance for engineering design, ultimately ensuring the safe operation of ultra-high voltage projects.