Abstract: The target architecture of ultra-high voltage, large capacity, and digitalized power grid poses new challenges to the field of high-voltage switchgear. To study the steady-state temperature rise of 550 kV/8 000 A gas insulated switchgear (GIS) and solve the problems of large model freedom and long calculation time when obtaining the temperature field, this paper investigates the thermal characteristics of a complete GIS bay model and constructs a temperature field reduced-order model based on the proper orthogonal decomposition (POD) method for digital twin applications. Firstly, the digital twin realization architecture for power equipment based on the Internet of Things is established, and a framework for digital twin-driven GIS state-awareness method is proposed. Based on this framework, a virtual entity model prototyping the GIS in the demonstration project of Zhuhai Northeast Station is constructed, and the distributions of magnetic density, loss, temperature, and airflow velocity at 8 800 A are analyzed; furthermore, a high-current temperature rise test platform is constructed for validation, and the experimental measurements are in good agreement with the simulation results. Secondly, the Latin hypercube sampling method is used to construct the input parameter sample set of the snapshot matrix of the model under different working conditions, and the POD method is further applied to the temperature field snapshot file to generate the temperature field downscaling model. Finally, the computational time and error of the model before and after the downscaling are compared: the computational time of the downscaled model is reduced from hourly order of magnitude to second compared with that of the full-order model, and the root-mean-square error of the model is 0.053% when the order is 6, which meets the requirements of the POD error specification. The results of this paper can provide supports for the design operation and maintenance of large-capacity switches, and provide a reference for the application of digital twin technology in the field of switchgear.