Objective To study AC corrosion behavior of aluminum for high voltage transmission line in 0.1mol/L Na2SO4 neutral solution. Methods the block corrosion specimens were cut from strain clamp and then were coated, polished and cleaned. Testing Tafel curve, AC impedance spectroscopy and corrosion rate of specimens under different AC density by self-made devices. Scanning electron microscope（SEM）, X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to observe and analyze the corrosion microstructure, elements distribution and corrosion products. Results Tafel curve move to negative direction at 0～40 A/m2, but reversed in 50A/m2 and then move to forward direction. AC impedance spectra also changed with increase of AC density, Nyquist diagram is gradually changed from single arc to double arc, appearing the Warburg impedance, the Bode-Phaze diagram from single peak to double peaks. The surface of specimens appeared corrosion pits and the layered shedding. Corrosion products are Al (OH) 3 and Al2O3. Conclusion The corrosion tendency of sample is deepened under alternating current. The corrosion surface has more pits, it is alternating between vertical corrosion and parallel corrosion, corrosion layer continuously formed and shed. Corrosion products is similar with generally aluminum corrosion products, they are Al (OH) 3 and Al2O3. Alternating current density the corrosion rate is relatively low when AC density less than 50 A/m2, but it increases above 50A/m2.