Abstract: The longitudinal cracks in the stainless steel elbow of the high temperature reheater were investigated by using the surface wave probe and the large angle longitudinal wave probe. According to the specifications and materials of the stainless steel pipe for high temperature reheater, the design principle of the probe, the detection principle of the stainless steel bend, the field inspection process and the defects wave characteristics were studied. The results show that the combination of surface wave probe and large angle longitudinal wave probe can detect cracks in the inner and outer wall of the stainless steel elbow.