Abstract: The welding process of Fe-30 Mn-8 Al-0.9C low-density steel was studied. A three-dimensional thermomechanical coupled finite element model was developed using Abaqus software. The thermophysical properties of the material were calculated by Jmatpro software. The influence of varying welding currents on the temperature field, residual stress and microstructure of the steel was systematically analyzed. The results show that the welding current has a significant effect on the distribution range and peak value of residual stress. At 190 A current, the residual stress distribution in the weld area is uniform and the peak value is low（580.2 MPa）; at 240 A current, the heat affected zone expands and the stress peak increases（593.1 MPa）; conversely, at 170 A current, the local stress concentration is caused by rapid cooling of the weld area. At the same time, the transverse residual stress exhibits greater sensitivity to current variations. The simulation validity is rigorously confirmed by experimental data: close agreement is observed between the numerically predicted and experimentally measured molten pool morphologies. The simulated temperature field accurately reflects the γ-austenite to κ-carbide and ferrite transformation temperatures occurring in the base metal during actual welding. Integrating experimental and simulation findings, a welding current of 190 A is identified as optimal for achieving a balance between stress uniformity and microstructural stability.