Abstract: In order to improve the insulation performance of basin-type insulator inside 550 kV GIS, this article optimizes the structure of the insulator. Firstly, based on finite element simulation, the electric field distribution and the mechanical performance of the original insulator structure are analyzed. Then, based on the Bernstein polynomial under the Bessel curve, the concave and convex shapes of the insulator are parameterized and reconstructed. Subsequently, a dual objective optimization model considering mechanical strength and electric field distribution is constructed, and the structure optimization of the insulator is achieved based on the non-dominated sorting multi-objective genetic algorithm (NSGA-Ⅱ). The optimal electric field distribution structure of the insulator under different mechanical strengths is obtained. The maximum field strength along the concave and convex surfaces of the optimized basin-type insulator and the maximum stress value of the body are both within the allowable values, namely, the maximum field strengths along the concave and convex surfaces are decreased by 11.63% and 12.87% compared to those of the original structure, and the mechanical performance margin is 1.11, which is decreased by 2.93%. This optimization method can be adopted to effectively improve the surface electric field distribution of insulators while meeting the mechanical strength requirements, which is of great significance for the structural design of basin-type insulators in GIS disconnectors.