Abstract: The formation of low pressure on the leeward side of the roof insulator under high-speed airflow will reduce the flashover voltage and affect the safe operation of the train. In order to improve the low pressure phenomenon on the leeward side of the roof insulator, the surrogate model is used to optimize the structural parameters of the roof insulator. The upper and lower tilt angles of the shed and the sheds spacing are selected as factors for the structural parameters of the roof insulator, and the minimum surface pressure on the leeward side of roof insulator is taken as the response. The full factorial experimental design method is used to obtain the sample data, and the main effects and interaction effects of the factors are analyzed. On this basis, a polynomial surrogate model is established to further obtain the best structural parameters. Finally, the effectiveness is verified by flashover experiments. The results show that the main effect of the upper and lower tilt angles of the shed are more significant than that of the umbrella skirt spacing, and there is no significant interaction effect between the factors. The optimal parameters are as follows: the upper and lower tilt angles of the shed are 8° and 0°, respectively, the shed spacing is 45 mm, the minimum surface pressure on the leeward side is increased by 25.62%, and the average pressure is increased by 42.47%. Under the wind speed of 100 m/s, the flashover voltage of the roof insulator is increased by 16.80%. The research results can provide reference for the design of roof insulator structure.