Abstract: With the continuous expansion of intelligent building scale and the increasing complexity of functions, traditional building electrical systems have gradually exposed limitations in operation perception, coordinated control, and operation and maintenance management. To improve the integration level and intelligence capability of building electrical systems, this paper introduces the Internet of Things (IoT) technology, constructs an intelligent building electrical system architecture based on the perception and execution layer, network transmission layer, edge computing layer, and cloud platform application layer, and studies key technologies such as heterogeneous protocol fusion, edge rule engine linkage control, and energy efficiency optimization. The implementation effect of the system is verified by engineering examples. The results show that the system can effectively improve operation and maintenance efficiency, enhance linkage control capability, and realize the safe, stable and energy-saving operation of the building electrical system.