Porous anodic alumina film (PAA film) was fabricated on pure aluminum in sulfuric/oxalic acid mixture electrolyte and was compared with the film prepared in single sulfuric acid electrolyte. Scanning electron microscopy (SEM) was employed to investigate the surface morphology, and the j-t curves were also recorded to analyze the formation process of porous anodic film. Uniform pores of high regularity were obtained in sulfuric/oxalic acid mixture electrolyte. With addition of oxalic acid in the electrolyte, PAA film with a diameter of 47 nm and thickness of 57 μm was obtained at 26 V. The film formation process includes three stages: formation of barrier layer, germination of micro-pores and stable increasing stage of porous anodic film. Porous anodic alumina film (PAA film) was fabricated on pure aluminum in sulfuric / oxalic acid mixture electrolyte and was compared with the film prepared in single sulfuric acid electrolyte. Scanning electron microscopy (SEM) was employed to investigate the surface morphology, and the jt curves were also recorded to analyze the formation process of porous anodic film. Uniform pores of high regularity were obtained in sulfuric / oxalic acid mixture electrolyte. With addition of oxalic acid in the electrolyte, PAA film with a diameter of 47 nm and thickness of 57 μm was obtained at 26 V. The film formation process includes three stages: formation of barrier layer, germination of micro-pores and stable increasing stage of porous anodic film.