In the aluminum alloy body of rail vehicle,the floor is a typical welded structure of aluminum alloy profiles. And after welding,it is prone to occur large residual stress and welding deformation,such as bulging and twisting,which increases the difficulty of assembly of various components,and reduces the bearing capacity of the floor. In this paper,a thermal-mechanical coupled finite element model based on the thermal-elastoplastic method is established and calculated to gain the postweld residual stresses and the distribution of welding deformations of floor structure. And the simulated residual stresses are compared with experimental results,which shows a good agreement. Finally,the simulations of different welding sequence of floor structure are compared and analyzed,and the welding scheme with the minimum welding deformation or residual stress is obtained,which provides a guidance for the welding practice.