Abstract: In order to explore the detection effect of the impact echo method in the detection of concrete defects of steel pipe lining, and the influence of the size of defects and the steel plate on the detection results, the physical model of the steel lining-self-compacting concrete was made in the laboratory, and the shock echo test was carried out on the steel lining side and the concrete side respectively. The test results show that the steel plate has an adverse effect on the impact echo method, which will weaken the detection resolution. In the same environment, the more shallow the depth of defect, the easier it is to be detected. The scanning impact echo test system can quickly determine the relative position and size of the defect.Therefore, when used in actual engineering, this method is suitable for initial measurement. In practical engineering application, the method can be used for large-scale preliminary survey, also can be combined with other methods for further determining the location and size of defects.