Bird damage is one of the important reasons for tripping or even outage of overhead transmission lines. The flashover process of bird manure is easy to develop to the angle steel of tower connection, resulting in angle steel damage, and the drainage line falls off. In order to improve the insulation level of insulation drainage line and ground wire or tower, reduce the probability of bird dropping flashover. Using COMSOL finite element simulation software, the three-dimensional simulation model of the electric field of the terminal head of the insulation drainage line is established. The influence of the insulation drainage line ' s material, the distance between the umbrella skirts and the inclination angle of the umbrella skirt on the electric field distribution of the insulation drainage line is studied. The results show that the distance between the terminal umbrella skirts has a great influence on the creepage distance of the insulation drainage line. The electric field distribution of epoxy resin and silicone rubber is similar, but the protective effect of silicone rubber is better. The research results can provide some reference for the insulation drainage line to suppress bird dropping flashover.