Abstract: Aiming at the problems existing in the current detection of high-pressure swing jet grouting cut-off wall, in this paper, the basic principle and process of elastic wave CT detection technology are introduced. The quality of high-pressure swing jet grouting cut-off wall of reservoir dam is tested, and core drilling and water injection test are applied in the part of the wall. The results show that the elastic wave CT has the advantages of fast detection speed and high detection accuracy in the quality detection of the cut-off wall, and it has a broad application prospect in the non-destructive testing of the cut-off walls quality.