Abstract: After welding, TC4 thin-walled structure shows large welding deformation.Welding with impacting rotation compression was utilized to solve this technical problem.The amount of impacting rotation compression stress is a critical influencing factor of the technology.In order to know the stress value, the measuring system including dynamic strain indicator, resistance strain gage and self-made base were developed to measure the complicated impacting rotation compression process.Based on the elastic deformation and energy conservation limitation, impacting rotation stress received by the TC4 thin plate was influenced by Young's module and thickness.Then, the loading distribution of the interface between impacting rod and thin plate was explained by finite element method.The stress relation between external loading and TC4 thin plate received was determined.