The invention discloses a GIL three-pillar insulator electrical performance optimization design method based on a particle swarm optimization algorithm. The method comprises the following steps: establishing an electric field finite element analysis model of the three-pillar insulator in a three-dimensional CAD software; determining the structure parameters and constraints of the key parts of thethree-pillar insulator to be optimized; establishing the electrical performance evaluation index of three-pillar insulator structure; constructing the objective function of structural optimization design of three-pillar insulator; using particle swarm optimization to optimize the structure of three-pillar insulator. The electric performance index of the key part of the three-pillar insulator are comprehensively considered, a method and a path are provided for optimizing the structure design of the three-pillar insulator with complex shape, the design period and cost of the three-pillar insulator are effectively reduced, the electric performance of the three-pillar insulator is improved, and the method has good practicability and economy.