Analytic procedure for dissimilar materials welding problem by using developed in-house solver is applied on butt and lap jointed model. In addition, the procedure of data transferring between commercial package and in-house solver for the preparation of input data for in-house solver has been developed. Therefore we can use the commercial package as pre and post processor for in-house solver and the results from in-house solver, for example, welding residual stress can be exported to commercial package as initial value to the model and then further analysis with the application of external loading can be carried out. For the similar material welding the welding residual stress has been decided by temperature dependent material properties that are input to the source program. In the case of dissimilar welding problem due to the difference of expansion and shrinkage rate between aluminum and steel there has been a slight variation in this dependency. Since the aluminum has large thermal expansion coefficient and the mechanical melting point is lower than steel, the order and level of mechanical behavior like stress history become different. The degree of mechanical deterioration of dissimilar materials welded model has been assessed with various view aspects, namely, welding residual stress, plastic strain, equivalent plastic strain and plastic work distribution and it has been revealed that Al5052 is mechanically more sever than SPCC for same heat input.