Abstract: X65 pipeline steel was welded by Tungsten Inert Gas Welding TIG using nickel base alloys (Arc625). For the welded joints, through the observation of microstructure, electrochemical test, hydrogen permeation test, four point bending and spectrum analysis of the H2S sulfide stress corrosion cracking (SSCC) behavior. The results showed that there were hard and brittle carbides in the fusion line. The electrochemical corrosion behavior of weld and HAZ was quite different, the selfcorrosion current density of welding seam is one order of magnitude smaller than that of HAZ. This kind of welded joint had strong hydrogen permeation resistance. After the SSCC test, the crack appeared at the fusion line, which was caused by the double effect of anodic dissolution and hydrogen permeation. The aggregation of C and the segregation of Ni and Cr at the fusion line had a great influence on the SSCC performance of the welded joint.