In order to give full play to the advantages of different materials under different operating conditions,transition layers were deposited by submerged-arc welding（SAW）,and butt joining between 28 Cr Mo Ni V and 25Cr2Ni4MoV were performed using narrow gap tungsten-arc welding（NG-TIG）combined with narrow-gap submerged-arc welding（NG-SAW）,thereby meeting the requirements of working condition of the steam turbine rotor. Tensile,bending,hardness and impact tests of dissimilar steel welded joints were carried out. The results indicated that the tensile strength of the welded joints is lower than that of the two kinds of parent materials,and the fracture locations are at the transition layers. And the hardness value of the welded joints is between 236 ,3,75 HV. Under the temperature conditions of-40 ℃,0 ℃ and 40 ℃,the toughness of BM2,HAZ-1,HAZ-2,SAW weld,BM-1 of welded joints increased in turn.