The friction stir welding process of 6005 A-T6 aluminum alloy metro floor was simulated by employing shrinkage strain method based on sequential thermodynamic coupling approach. In order to obtain the shrinkage strain,a thermal elastic-plastic finite element analysis of the local structure of the floor was carried out firstly by using equivalent heat source model and sequential thermodynamic coupling method. The welding induced distortion of the floor was calculated according to the obtained shrinkage strain,and the calculated results were compared with the experimental measurement results. The comparison results show that the welding deformation trend calculated by finite element method is highly consistent with the actual measurement results,and the error between calculated and experimental measurement results is within 0.5 mm. It is verified that the employed methods in this paper are feasible for predicting FSW welding induced deformation of large components. Then,the reasonable mitigating process of welding induced deformation should be adopted for the large FSW welded structures,such as the aluminum alloy floor of metro vehicles mentioned in the paper.