Abstract: In order to improve efficiency,accuracy,intelligence and reduced manpower for tunnel secondary lining quality inspection,in this work, the principle and method of tunnel secondary lining inspection by impact-echo method were clarified,and the intelligent inspection system for tunnel secondary lining quality by impact-echo method was developed.The system includes a impact-echo detection module,a mobile platform and segmented track module,an automatic acquisition and intelligent data interpretation module,and two flexible equipment mounting modes.It has the advantages of anti-reinforcement mesh interference,stable stimulation,strong applicability,flexible mounting mode,wide detection range,and automated operation with reduced manpower.Efficient and intelligent recognition of tunnel secondary lining thickness and defects can be achieved.The application results relying on a plateau railway tunnel engineering show that the average relative error of the system’s thickness detection was 1.36%,and the average of quality defect identification accuracy was 87.5%.The system has a broad application prospect in the field of tunnel secondary lining quality inspection.