Abstract: There are various materials and structures in compound board welded joint and it is difficult to detect them by usual methods. Unrelated display is liable to be misjudged as related display. A method integrated by magnetic particle Inspection, penetration inspection and ultrasonic inspection was put forward. The results showed that related display was found in layer welded joint of compound board, and unrelated display was found in dissimilar steel transition layer welded joint. Various inspection methods should be considered in case of mistake caused by single method.