The　work　aims　to　provide　support　for　safe　operation　of　pipes.　Based　upon　polarization　curve　method　and　electrochemical　impedance　spectroscopy　(EIS),　systematic　experimental　and　theoretical　studies　were　applied　to　cathodic　protection　parameters　of　X65　and　X80　pipeline　steels　in　Dagang　simulated　soil　solution　by　building　indoor　experimental　system.　According　to　the　polarization　curves,　cathodic　protection　potential　of　X65　pipeline　steel　ranged　from-400　to-1200　mV,　and　X80　pipeline　steel　from-400　to-1150　mV.　Relationship　between　charge　transfer　resistance　Rt　and　cathodic　polarization　potential　Ee,c　was　studied　based　on　the　EIS　results,　it　was　found　that　hydrogen　evolution　potential　and　optimum　protection　potential　of　X65　pipeline　steel　in　Dagang　simulated　soil　solution　was-970　mV,-850　mV,　respectively;　and　for　X80　pipeline　steel,-960　mV,-800　mV,　respectively.　Therefore,　it　can　be　concluded　that　hydrogen　evolution　potential　of　X65　pipeline　steel　was　less　than　that　of　X80　pipeline　steel.　Cathodic　protection　parameters　of　X65　and　X80　pipeline　steels　are　verified　in　Dagang　simulated　soil　solution,　and　hydrogen　evolution　potential　and　optimum　protection　potential　of　X65　pipeline　steel　are　both　less　than　those　of　X80　pipeline　steel.　The　studies　have　provided　certain　theoretical　basis　for　cathodic　protection　of　X65　and　X80　pipeline　steels.　©　2018　Chongqing　Wujiu　Periodicals　Press.　All　rights　reserved.