Abstract: Objective In order to promote widespread application of ultra-thin TA1/304 dissimilar metal joining structures, a novel combined joining method was developed for ultra-thin TA1/304 dissimilar metals. Methods According to metallurgical compatibility of alloy elements, niobium was selected as a metal transition section. Titanium welding wire was used to weld TA1/Nb plates. Aluminum bronze welding wire was used to weld Nb/304 plates. Butt gap between Nb/304 plates was 1 mm and aluminum bronze welding wire pointed towards Nb plate. Gas metal arc welding was used to fabricate TA1-Nb-Cu-304 combined joining structure. Microstructure and composition distribution of each zone of ultra-thin plate welded joints were analyzed by metallographic microscopy, scanning electron microscopy and energy dispersive spectroscopy. Results The results showed that welding process was stable, weld had sound appearance and boundaries of each zone of weld were obvious. Cu based weld effectively isolated Nb element from Cr, Ni, and Fe elements of 304 stainless steel, avoiding the formation of intermetallic compounds. Tensile strength and elongation of TA1/Nb butt joint was 326 MPa and 18.5%, respectively. Fracture was located on TA1 base metal. Tensile strength and elongation of 304/Nb butt joint was 467 MPa and 22.1%, respectively. Fracture was located on Nb transition section. Conclusions The developed dissimilar metal combined joining process can avoid the formation of brittle intermetallic compounds and achieve reliable joining of ultra-thin TA1/304 dissimilar metals.