Under the rainfall environment, the electric field strength on the contact network insulator surface is distorted, which is detrimental to the normal operation of the high-speed railroads power system. To study the correlation between water droplets and insulator electric field characteristics, the electric field distribution on the surface of contact network insulators was simulated in multi-physics field simulation software. The effects of different water droplet parameters on the electric field distortion characteristics of the contact network insulator surface were analyzed with the electric field distortion rate as the evaluation criterion. The results showed that the presence of water droplets caused a severe distortion of the electric field. The water droplet spacing has the greatest effect on the distortion characteristics of the electric field, which is about 275%. Therefore, it is of great importance to analyze the influence of water droplets on the insulator surface on the field strength distribution under the rainfall environment.