In this work 7kw CW CO2 low order mode laser was utilized in the deep weld of high-speed steel (W18Cr4V) and spring steel (65Mn). By using the metallography microscope, scanning electron microscopy and bending strength test, the microstructure, micro hardness and fracture profile of the welded joint with different welding technology were analyzed, and then its fracture property as well as the relationship between structural transformation and strength were discussed. Finally, on the basis of the comparison and analysis of processing property, an advanced welding technique that can obviate the welding defect was presented.