Porcelain insulator corrosion seriously threatens the safe and stable operation of transmission lines. In this work, the corrosion behavior of porcelain insulator steel caps in NaHCO3 solution, NaCl solution, and dust filtrate was investigated by electrochemical method, and the electrochemical impedance spectroscopy and polarization curve analysis showed that the electrochemical corrosion rates of NaHCO3 and NaCl solution on porcelain insulator steel caps were positively correlated with the solution concentration, the corrosion rate of steel caps was the largest in NaCl solution, and the corrosion rate in the dust filtrate increased with the increase of pollution equivalent salt density. Among them, the corrosion rate of the filtrate of contamination in the highly polluted degree area was close to that of the low concentration NaHCO3 solution. Through the comparison of the color and micromorphology of the corrosion experimental solution, it can be found that there was a deposition of corrosion products and oxidation products on the surface of the sample in NaHCO3 solution and dust filtrate, while comprehensive corrosion occurred on the corrosive surface in NaCl solution, and no obvious brown-red Fe(OH)3 deposition occurred. Therefore, the anti-corrosion of insulator metal accessories in highly polluted areas was of great significance to prevent insulator failure and pollution flashover.