Abstract: By using water immersion focusing method in an ultrasonic C-scan inspection system, the quality of Cu/steel surfacing weld was evaluated.The sound field in the two planes of axial and radial to the cylinder were analyzed when the sound beam vertically incidents into the cylindrical work piece.Based on the above theoretical analyses, surfacing welds were inspected by C-scan mode.In order to verify the reliability of ultrasonic test, ultrasonicA-scan signals received from typical area of the workpiece were studied and the corresponding destructive test was done.The result shows that it is feasible to evaluate the surfacing weld by using the proposed method. Moreover, the tested result is more reliable when sound beam incidents into the piece from the base metal.