This Recommendation describes the architecture of the digital twin system in power grid. The digital twin power grid is a digital representation of the power grid, achieved through real-time interactive mapping and continuous synchronization with its physical counterpart. The digital twin system supports the management of the digital twin power grid by collecting multi-source data, managing digital twin models and providing standardized interfaces. Through the digital twin system in power grid, it enables monitoring, analysis, prediction, optimization and decision-making support for power grid operations across its life cycle stages.