The　corrosion　mechanism　of　X80　steel　in　simulated　solutions　of　acid　red　soil　and　product　oil　sediment　under　mechano-electrochemical　interaction　(MEI)　was　researched　to　build　a　new　finite　element　model　through　multi-physical　field　coupling　simulation　technology.　Based　on　the　new　model,　the　effect　of　external　wall　defect　growth　on　the　internal　wall　corrosion　of　oil　pipelines　was　analyzed　in　detail.　The　results　showed　that　the　distributions　of　stress　and　corrosion　of　the　internal　wall　were　extremely　affected　by　the　external　wall　defect　depth,　and　the　corrosion　rate　of　the　internal　wall　was　enlarged　remarkably　by　the　external　wall　defect　growth.　Moreover,　attributing　to　the　local　galvanic　cell　effect　under　MEI,　the　growth　rates　of　corrosion　defects　in　the　depth　and　length　directions　of　the　external　defect　were　accelerated　because　these　directions　were　associated　with　larger　stress　and　equivalent　to　the　anode,　but　the　corrosion　rate　in　the　width　direction　of　the　external　defect　was　inhibited　because　this　direction　was　associated　with　smaller　stress　and　equivalent　to　the　cathode.