The system adopts fast phased array, multi-channel high-speed data processing and guide wheel automatic alignment technology to realize intelligent diagnosis of typical defects such as rail head damage, screw hole crack, rail waist and rail bottom crack, and carry out automatic positioning, feature extraction and automatic alarm for defects. It can replace the existing wheeled large rail flaw detection vehicle and manual rail flaw detector. And it is applicable to the automatic detection of various types of rails in domestic railway.