Abstract: Miniaturization and environmental protection are the essential development trend of electrical equipment. To this end, the paper carries out a multi-objective optimization study aimed at reducing the structural size of the GIL pipeline. Initially, the basis of GIL gas room insulation judgment was proposed, a multi-physical field coupling model for assessing the insulation margin of GIL gas room was established, the influences of GIL pipeline structural parameters on insulation and temperature rise performance were analyzed, and the optimization parameters of GIL structural dimensions were extracted. Based on the consideration of insulation performance, temperature rise performance, and cost of size optimization of GIL gas room, a multi-objective optimization study of pipeline structure was carried out. The response surface model was used to fit the functional relationship between the structural parameters and the GIL field strength and temperature rise, while the optimization objective and the corresponding constraints were determined, and the NSGA-Ⅱ algorithm was used for the optimization-seeking calculation of the structural parameters. The results show that, through optimization, the optimized GIL pipeline size can be reduced by 10%, the insulation margin of the GIL gas room is improved by 6%, the temperature rise is decreased by 19.6%, the manufacturing cost is reduced by 34.6%, and the overall optimization effect is good. The research provides a useful reference for the development of GIL miniaturization.