Abstract: Three types of sulfuric acid solution with different concentrations were designed and the main factors affecting the hard anodic oxidation of 6061 aluminum alloy were studied by neutral salt spray test. The results show that the concentration of sulfuric acid in the range of 120~180 g/L has no obvious effect on the salt resistance of the film after sealing. Under the test condition of this research, the larger the current density, the higher the trough voltage is. The current density has a linear influence on the film thickness but has little effect on the hardness of film. The temperature of the bath has great influence on bath voltage:the lower the temperature is, the higher the bath voltage is, and in the later period of oxidation, the voltage rises rapidly.The bath temperature has a great influence on the color of film surface but has no obvious effect on the thickness and hardness of film.