The　effects　of　stray　alternating　current　(AC)　on　the　corrosion　behavior　of　X70　high　strength　pipeline　steel　in　a　marine　soil　simulated　solution　was　investigated.　For　a　comparison,　the　study　was　operated　in　3.5%　NaCl　solution　and　with　an　application　of　150　MPa　tensile　stress　as　well.　The　electrochemical　measurements　of　open　circuit　potential　(OCP)　and　potentiodynamic　polarization　were　used　to　exam　the　electrochemical　process　on　the　X70　steel　surface　under　AC　interference.　A　digital　camera　and　scanning　electron　microscope　(SEM)　were　used　to　analysis　the　corrosion　morphology.　The　results　show　that　a　30　A/m(2)　AC　interference　slightly　shifted　the　corrosion　potential　-0.03　V,　while　a　300　A/m(2)　AC　signal　changed　the　value　as　much　as　-0.2　V.　It　was　well　explained　with　a　mathematic　model　of　AC　interference.　The　corrosion　rate　increased　with　the　AC　current　density　in　all　test　conditions.　A　corrosion　mechanism　was　proposed　to　describe　the　occurrence　of　AC　corrosion　on　the　X70　steel　sample　surface.　A　net　anodic　current,　implying　an　anodic　dissolution,　was　resulted　from　a　complete　cycle　of　AC　interference.　The　corrosion　morphology　changed　from　uniform　corrosion　to　pitting　corrosion　under　the　AC　interference.　Thus,　stray　AC　promoted　the　localized　corrosion.