To　study　lithium　ion　battery　state　of　health　(SOH),　according　to　the　definitions　of　SOH　and　state　of　charge　(SOC)　and　2RC　(resistance-capacitance)　battery　equivalent　circuit　model,　the　SOH　estimation　model　of　the　battery　voltage　curve　based　on　the　constant　current　charging　stage　was　established.　Based　on　the　analysis　of　the　battery　cycle　life　test　data,　the　SOH　was　estimated　by　the　battery　voltage　curve　of　the　constant　current　charging　stage　and　compared　to　the　testing　data.　The　relative　error　of　SOH　estimation　was　in　the　range　of　2%　before　the　SOH　value　was　reduced　to　80%,　which　was　well　consistent　with　the　experimental　results.　The　results　show　that　the　proposed　method　is　feasible　and　accurate.　©　2016,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.