The method was performed on the C-scan image of flat-bottom hole. The experimental results show that the defect edge can be detected rapidly and accurately. It is more adaptive for the edge detection of ultrasonic C-scan image than Sobel algorithm and Canny algorithm. 对平底孔超声C扫描图像边缘检测的试验结果表明,该方法适用于超声C扫描图像的边缘检测,明显优于Sobel算法和Canny算法,能够快速准确检测出缺陷边缘。