Abstract: Residual stress is one of the most important challenges to the safety of parts and structures as welled.Ultrasonic stress measurement system is modified for the measurement of thin wall welded structure.The residual stress of high-speed train body structure is measured by the system.The measurement process is not only nondestructive, but also real-time and quick.The results of the ultrasonic method are verified by the laser hologram interference hole-drilling method and finite element method.The deviations of the results are also discussed.