Abstract: An axisymmetric finite element model was developed to simulate the contact status between electrode and sheet and between sheet and tube during the squeeze stage of sheet-tube single-sided spot welding.Some influencing factors on the contact region and pressure distribution were discussed.Analyses showed that the squeeze stage of sheet-tube single-sided spot welding has great difference from that of the traditional spot welding.By the results,there exist ring contact regions between the electrode and sheet and between sheet and tube which are different greatly and will get a ring nugget after welding.The contact region between the electrode and sheet is determined by electrode end size rather than pressure,but that between the sheet and tube is determined by pressure as well as electrode size.In addition,comparison of the analytic results to test data using servo gun are presented and discussed.The simulated results are in good accordauce with the experiments.The stuties offer the proof for the parameter optimization in body light weight and nugget quality control.