Abstract: T91 and 15-15Ti are candidate structural materials for sodium and lead bismuth cooled fast reactor of the fourth generation nuclear energy. The welding properties, post weld heat treatment and welding stresses of Ferritic/martensitic steels and austenitic steels have been extensively studied at home and abroad. In this paper, the microstructure and mechanical properties, heat affected zone (HAZ) and base metal of T91/15-15Ti dissimilar steels welded joint were studied for as welded and heat treated plates, which provides experimental data of parameters selection and material application for T91 and 15-15Ti dissimilar steels welding.