The Dss2205/X65 bimerallic plate were welded by the fiber laser，the means of OM were used to observe the microstructure of welding joint. The distribution of the Cr element in the welded joint were studied to infer the fluidity of molten pool. The potentiodynamic scanning method was carried out to measure the anodic polarization curves of DSS2205base metal and the welded joint. The experimental results show that the microstrucure of the welded joint exhabits a typical hierarchical characteristic along thickness direction of welded joint.The Cr distribution in the welded joint shows that the fluidity of molten pool possess the characteristics of Marangoni convection,the Molten metal in Molten pool tend to spread upward flow, and less affected by gravity.Polarization curves show that the corrosion potential between the composite layer of joint and the DSS2205 base metal is same, but the pitting potential of welded joint are lower than that of the base metal DSS2205. Polarization curvesn also show that the joint welded by laser beam with a small focusing spot size shows a better point corrosion resistant ability compared with the joint welded by laser beam with a big focusing spot size.