Abstract: There are various repairing processes for keyway wear. In the use of welding repair, attention should be focused on the welding quality to avoid mechanical performance degradation of the shaft head due to welding defects, leading to a non ideal repairing effect.In this article, phased array ultrasonic technology is applied to the workpiece defect simulation and three dimensional dynamic display function, and it has realized effective and accurate quantitative detection of weld defects of the motor rotor welding repair parts within the keyway. Present work may provide a new way of thinking for axial keyway surfacing welding repair test.