The utility model provides an attach fitting structure for automobile assembling belongs to automobile manufacturing technical field. Joint strength waited technical problem inadequately when it had solved the assembly of current car side wall and top cap. This attach fitting structure includes the bottom plate of bar, the vertical diaphragm of a plurality of intervals setting and the vertical plate that a plurality of interval set up of setting firmly on the bottom plate, and the diaphragm sets up with vertical plate is crisscross, the diaphragm has still set firmly the connecting plate withvertical plate's upper end, all is equipped with expansion glue on the bottom surface of bottom plate and on the upper surface of connecting plate. The utility model discloses through diaphragm and the crisscross played a supporting role that sets up of vertical plate in the well attach fitting structure to while and side wall and header connection, thus whole torsional rigidity and the torsionalmode that the local stiffness of body structure had promoted the automobile body improved, the inside hollow structure that is of this attach fitting structure, the inner panel and the outer plate thickness of simultaneously all right attenuate side wall joint department have been realized the synchronous of weight reduction effect and NVH performance and have been improved.