Abstract: In this paper, we present a virtual training system which realistically represents the situation of real welding. First of all, we built a database about welding outputs such as the shape of bead which is the deposit outcome resulting from inputs of real welding conditions and operations. Second, we performed an analysis of relations between input variables and output variables, and the major and minor factors influencing on the welding shape were classified. Finally, we designed an estimation process of outputs by various inputs such as user's movement, and constructed the method of graphical representation for real-time visualization from heuristic sources. Additionally, we also installed a welding simulator for a teacher and trainees, which can support not only a variety of welding situations but prompt evaluation of results and educational guide by optimal welding conditions.