Abstract: Based on micro-hardness tests and microstructure analysis of welded joints, welding softening character of A6N01S-T5 aluminum alloy were studied. According to welding temperatures and micro-hardness in different regions of the welded joint, the softening model of A6N01S-T5 aluminum alloy was established. In order to simulate the welding process of train roof in high-speed train, a quick welding simulation method was developed based on an average temperature curve method. A welding experiment of typical welded joints was carried out. The welding process was simulated with a moving heat source method and the average temperature curve method, respectively. The results show that compared with the measured deformation and the residual stress, the average temperature method can replace the moving heat source method to simulate the welding process. The softening model and the average temperature curve method were applied to simulate the welding process of roof of A6N01S-T5 aluminum alloy train, a well agreement was obtained between the calculated and measured values of the welding distortion in the train roof.