CATIA CAA object extension is the most important way of self-defined object creation and is also the difficulty of development. Based on analysis of processing parameters and restrains of resistance welding, a framework for welding spot modeling via the technical route of CAA user interface design, self-defined object, parameter validation and entity creation, is advanced. Furthermore, problems of parameter automatic computing and validation are studied through examples of spot diameter computation of nut side weld and distance computation between spot center and sideline. Finally, parametric modeling of plate projection weld and nut weld of resistance welding of resistance welding for vehicle seat framework (VSF) is realized by CATIA CAA redevelopment, which improves weld design efficiency of VSF parts and provides fundamental for multi-type welding (including spot welding, arc welding, etc.) management system development.