This fundamental research presents an investigation of Wire Arc Additive Manufacturing (WAAM) process on distortion and residual stress using numerical simulation. Further, WAAM geometry was modeled using simplified rectangular bead shape with five layers and three strings. The thermo-mechanical numerical simulation is conducted under consideration of non-linear isotropic hardening modeled by using general purposed FEM software MSC Marc/Mentat. In this simulation, different heat source models (Goldak's double-ellipsoid and rectangular) are implemented and compared, whereby the later model was to be developed by using subroutine provided in the software. For analyzing the residual stress, separation technique between wall and substrate was introduced after the cooling down period. The outcome of this research is to develop an effective procedure to analyze the distortion and residual stress of wire arc additive manufacturing of stainless steel.