Abstract: A calculating formula of Gaussian model in triple-electrode welding is derived according to arc configuration and the superimposition principle of heat resource, and the proper finite element model is constructed. Then the transient change of temperature field of T-joint is simulated and analyzed in tripleelectrode high speed welding process with the boundary conditions of convection, radiation, evaporation, fluid flow and latent heat of phase change being fully considered. Finally, the simulated results are being analyzed and checked out with experiment. The results showed that the calculated shape of weld cross section was coincident with the actual results and weld thermal cycle was coincident with the fine texture results which had also validated the dependability of the above-mentioned model.