Abstract: Thick-walled pipes have been widely used in the field of petrochemical and nuclear power and its rapid detection evaluation technique has received extensive attention of the domestic and international scholars.As to the thick-walled pipe which outside diameter is 269 mm and its wall thickness is 32 mm, the dispersion curves of circumferential Lamb wave were calculated by the Disperse software.In order to detect defects of different thickness, three different artificial defects which were located in outer wall, middle thick wall and inner wall separately were made.According to the dispersion curve, 0.5 MHz excitation frequency was selected, the experimental research of thick-walled pipe's defect detection was carried by using circumferential guided waves with different wedge incident angle in this paper.The experimental result shows that when the wedge incident angle was 55°, the defects located in outer wall and middle thick wall could be detected and the detection sensitivity of external wall defect was the highest, but the defect located in the internal wall was difficult to detect;when the wedge angle was 37°or 45°, the defects located in outer wall,middle thick and inner wall could be detected, and the detection result of inner wall defects with angle of 37°is the best.