In order to improve the anti-fouling characteristics of the electric insulator for electric railway, a functional coating for preventing pollution was carried out on the surface of the T type post insulator and long rod insulator in the railway insulators. In order to ensure the durability of the thin film on the coated insulator surface, the coating was annealed at three different annealing cases by using a furnace. Case 1 is annealing treatment at 250°C and case 2 is annealing treatment at 400°C. Case 3 is the double annealing treatment (case 1 + case 2). The film Surface conductivity and anti-fouling characteristics of the insulators annealed at three temperature conditions were measured. It was confirmed that the insulator annealed in case 3 had both good conductivity and anti-fouling characteristics.