Abstract: Residual stresses are one of the most important challenges to the safety of welded structures.Ultrasonic stress measurement installation was modified to meet the measurement of thin wall welded structure.The residual stress of LY12 body structure of high-speed train was measured by this system.The measurement process is not only nondestructive, but also real-time and quick.The measuring result of the ultrasonic method is verified by laser hologram interference hole-drilling method and finite element method.The deviations are also discussed.