To reduce the probability of such flashover accidents caused by bird droppings， a new type of insulated coated drainage line was developed. This line utilized high-performance silicone rubber insulating materials to fully coat the steel-cored aluminum strand， and an umbrella skirt was installed on the surface of the drainage line. Simulation analysis was conducted to examine the influence of the silicone rubber insulation layer and bird droppings on the spatial electric field distribution of the drainage line. The flashover characteristics of insulated coated drainage lines against bird droppings were studied by simulation test. The simulation results show that with the increase of the thickness of the insulating layer， the surface electric field intensity decreases gradually. As the thickness of the semiconductor layer increases， the electric field intensity on the surface of the drainage line decreases. The test results show that the insulation layer coated by bare wire can significantly improve the insulation performance of the drainage line， and the silicone rubber insulation coating is obviously better than the buckled silicone rubber insulation sheath. Every 1 mm increase in the thickness of the silicone rubber insulation layer results in breakdown voltage increases of about 10.7 kV， and the semiconductor layer can further improve the insulation performance. The umbrella skirt can effectively prevent the spread of the arc on the surface of the insulated coated drainage line.