The　ground　conductor　is　prone　to　corrosion,　which　affects　its　ability　to　diverge　current　and　the　normal　operation　of　the　power　system.　The　traditional　detection　method　can＇t　detect　its　corrosion　degree　intuitively.　This　paper　proposes　a　novel　method　based　on　Electromechanical　impedance　(EMI)　technique　to　evaluate　the　corrosion　degree　of　the　grounding　conductor.　Firstly,　based　on　the　analysis　of　corrosion　of　metals.　The　change　of　ground　conductor　radius　Delta　r　is　used　as　the　corrosion　parameter.　A　linear　model　of　peak　frequency　Delta　fm　and　corrosion　parameter　Delta　r　in　asymmetric　layout　is　established　by　analysing　EMI　and　conductor　mechanical　admittance.　Secondly,　the　EMI　coupling　models　with　different　sensor　layouts　were　built　on　the　finite　element　software.　It　is　verified　that　the　asymmetric　sensor　layout　effectively　improves　the　sensitivity　to　corrosion.　The　linear　model　greatly　improves　the　assessment　accuracy　compared　with　the　Mean　Absolute　Percentage　Deviation　(MAPD)　and　Root　Mean　Square　Deviation　(RMSD)　damage　index.　Thirdly,　the　proposed　method　is　verified　in　a　real　grounding　conductor　corrosion　experiment.　The　method　based　on　the　EMI　technique　with　asymmetric　sensor　layout　can　evaluate　the　corrosion　of　the　grounding　conductor　well.