Abstract: The strip defects were found on the surface of low magnification sample from longitudinal beam forgings of MB15 deformation magnesium alloy.The qualitative analysis on the defects was carried out by means of fracture analysis, metallographic examination and energy spectrum analysis.The results showed that the defects were caused by zirconium element segregation, which was distributed longitudinally along the part deformation distribution during die forging, the defects were exposed along flow direction after corrosion.