Abstract: In a humid environment, the electric field on the insulator surface will be distorted by the water droplets condensed on the insulator surface. In this paper, the FXBW 4-10/100 composite insulator was taken as the research object. The electric field of the insulator with or without water drops under 10kV DC voltage was simulated by COMSOL software. The influence of the water drop related parameters (particle sizes, spacing, conductivity, and relative dielectric constant) on the electric field distortion characteristics of the insulator surface was analyzed with the electric field intensity and its distortion rate as the evaluation criteria. The results show that the electric field intensity on the surface of the water drop is much higher than that around it, while the electric field intensity inside the water drop is much lower. The particle size, spacing and relative permittivity of the water drop all have a great influence on the distortion of the electric field strength on the insulator surface with the distortion rate is even up to 573%, while the influence of the conductivity is small. The farther the water drop is from the central axis of the insulator, the higher the electric field intensity. The areas with high distortion rate of field strength are mostly concentrated at the edge of the composite insulator, which is easy to cause pollution flashover.