Abstract: Local black stripes were found on the surface of aero seat products of 7075 aluminum alloy after anodic-oxidation treatment. Macro and micro observation, chemical composition analysis, metallographic structure analysis, hardness testing, and energy spectrum analysis were carried out to find out the cause. The results show that the homogenization treatment of 7075 alloy rods was not sufficient, and massive second phase distributed like bonds along the direction of extrusion, which was difficult to dissolve in the Al matrix in the subsequent heat-treatment. Besides, the smaller extrusion ratio of the extruded sheet and the improper tonnage selection of extrusion press caused the existence of cast structure in the matrix and the massive second phase being not fully broken.