Abstract: A bright line on the side center of the middle frame product of the 6063 aluminum alloy which product after warm extrusion. Anodizing can still not eliminate this bright line. Chemical composition analysis, metallographic examination, hardness testing, scanning electron microscopy and energy spectrum analysis were used to analyze the cause of the bright line on the side of the aluminum alloy products. The results show that the deformation rate of the aluminum alloy was too large during warm extrusion, which makes the middle layer residual larger internal stress. Due to the uneven distribution of internal stress, the bright line area was formed, and the microcracks caused by stress cracking were formed in the bright line region. During the temperature extrusion process of aluminum alloy, the heating temperature and the deformation rate are controlled, and the timely recovery and recrystallization of the tissue can be ensured, which can effectively avoid the production of the bright line.