Abstract: Creep and creep fracture tests for the macro mechanical heterogeneous dissimilar steel welded joints fabricated by flash butt welding with high strength match (B_M-W_H-B_L),low strength match (B_H-W_L-B_M) and medium strength match (B_L-W_M-B_H) were carried out respectively.The mechanical factor of creep fracture for different strength match joints was analyzed by finite element method.The results indicated that the fracture occurred along the low strength base metal or weld metal adjacent to the weld interface for high strength match and low strength match joints,and showed a brittle character.However,the creep fracture of medium strength match joint,located in the low strength base metal remote from the weld interface,showed a ductile fracture character.The stress triaxiality was a major mechanical factor which induced brittle fracture,and the strain concentration controlled the ductile fracture procedure.