Abstract: Through the analysis of positional error during ultrasonic shear wave propagation in the clad steel plate′s butt welds, conclusions were drawn for the ultrasonic testing′s positional error compensation rules and the positional error compensation method was also given. Comparison tests of positional error compensation have been done for the surface defects and internal defects in the clad steel plate′s butt welds. An ultrasonic detection method of simple operation and accurate defect locating was summarized for the clad steel plate's butt welds.