Abstract: In this paper the welding characteristic, welding process, testing condition of 45 and 40Cr steel are introduced.The test result indicates that the welding process and method adopted is appropriate to the welding of dissimilar steels 45 and 40 Cr.The performance of the butt welded joint of these two steels is equivalent to the mechanical properties of 45 steel at annealed state and the welding procedure, can be used for production in batches.