Abstract: A three-dimensional 3D finite element model of Q235 low carbon steel plate butt joint was established to study the effects of different plasma currents on welding penetration, temperature field and residual stress of Q235 steel. The combined volume heat source model of the double ellipsoid heat source model and the three-dimensional cone heat source model was used to simulate the plasma-MIG hybrid welding heat source, and the accuracy of the numerical simulation was verified by the experimental results of the butt welding process of the Q235 steel plate. The results show that the numerical simulation results of the weld pool morphology of the weld section are in good agreement with the experimental results, and the heat source model can reliably simulate the combined effect of the two heat sources of plasma and MIG arc. The effects of plasma current on the temperature field and stress field of plasma-MIG hybrid welding were studied with different plasma currents as factors. The results show that the plasma current can effectively increase the penetration and reduce the high residual stress concentration area.