Abstract: The CO₂ corrosion behavior of 3Cr low-alloy pipeline steel and its weld joints were researched with a high-pressure high-temperature autoclave and electrochemical techniques.The results showed that the corrosion product scales enriched Cr element were compact,which is the main reason that the CO₂ corrosion resistance of 3Cr low-alloy pipeline steel is superior to that of X65 steel.The product scales of the base metal,heat affected zone (HAZ) and weld metal in 3Cr low alloy pipeline steel weld joints were similar with each other,with Cr enrichment and compact structure.Compared with X65 steel,the corrosion potential of 3Cr low alloy pipeline steel was more positive and the corrosion current density was lower.The base metal of 3Cr low alloy pipeline steel weld joints as an anode would be suffered corrosion firstly,and the weld metal and HAZ of the weld joints as cathodes would be protected.