Abstract: Conventional piezoelectric ultrasonic technique can not be used to measure the wall thickness of natural gas pipeline, in which there is no coupling medium. In this regard, a wheeled ultrasonic wall thickness measurement system is developed. This system consists of wheeled thickness measuring probe, ultrasonic excitation and receiving circuits, data analysis & storage units and other interface circuits. The wheeled ultrasonic probe is adopted to measure the pipeline wall thickness. As to the system design, the piezoelectric ultrasonic transducer is mounted on wheel hub, which outside is casted with elastic materials; wheel surface and tested specimens are closely fitted to achieve the ultrasonic sound field coupling. The pull test results show that this system is stable, and the wheeled ultrasonic probe and the pipe wall are well coupled; it can discern all wall thickness values, with accuracy up to 0.1 mm. This system can be integrated into the pipe deformation, corrosion and crack detectors.