Abstract: A numerical simulation system of welding was developed for studying welding thermal process,welding stress/strain and welding deformations. A mesh-oriented data modeling method was applied to solve the problem which is too difficult to use normal FEM software to simulate welding thermal process,stress/strain and deformation of typical aircraft components. The simulation system was designed by using object-oriented method. Operating the system,a customer could simply input the geometry parameters,such as mesh size,welding thermal source parameters,fixing position and welding sequence,into the user interface. All the data input were changed into auto simulation information through the calculation of the system core class. After that,the auto simulation information was converted into Marc command stream which would be loaded by the wheeling Marc process on the background,and calculating the result data of welding thermal process,stress/strain and deformation can predict and analyze the welding stress and deformation.