<p>Welding process simulation is applied at the design stage to increase the reliability of the assembled final structure. To improve the accuracy of welding thermal deformation analysis, it is important to define an accurate welding heat source model. Plasma arc welding (PAW) shows characteristics of both arc and laser heat sources, making it challenging to select appropriate heat source models and parameters. Due to these difficulties, there are few references for thermal deformation analysis for PAW. This study describes the effect of Gaussian parameters of PAW heat sources on temperature distribution and thermal deformation analysis. A conical heat source was defined by combining a volumetric heat source and a surface heat source, and analyses were performed by changing the Gaussian parameters of the surface heat source. Changes in Gaussian parameters affect the size of the heat source, which in turn affects temperature distribution. As a result, Gaussian parameters influence the concentration of the heat source, the width of the heat-affected zone, and the quantitative magnitude of thermal deformation.</p>