The digital ultra-high voltage (UHV) substation system collects data from the full system in zones I/II/IV of the substation, based on panoramic data acquisition and driven by digital technology. It fully utilizes new technologies such as digital twinning, virtualization, containers, and big data, and aims to achieve the full-chain digitalization of “equipment status, operation site, and professional management”. It builds a digital operation and maintenance control system for UHV substations with multi-dimensional data fusion, hierarchical business collaboration, unified interface specifications, and convenient application expansion. It achieves panoramic twinning management, early warning, and intelligent diagnosis of UHV substation equipment through functions such as equipment status overview, equipment alarm overview, event-based alarm, auxiliary equipment monitoring, equipment active early warning, fault handling auxiliary decision-making, training drills, warehouse management, data management, and intelligent safety measures. It improves the operation and maintenance monitoring strength, production informatization level, and management lean level of UHV substation equipment. This article introduces the background and principles of the construction of digital UHV substation systems, and designs the system from three aspects: overall architecture, data architecture, and technology and application architecture. It is applied in practical construction, providing a reference for the promotion, optimization, and upgrading of digital UHV substations.