Based　on　mass　balance　principle　and　simultaneous　equilibrium　principle,　the　metal　element　Me　(Co,　Ni,　Fe,　Mn),　complexing　agent　of　OH-　and　NH3,　and　precipitant　of　OH-,　S2-　and　CO32-　were　chosen　to　form　the　complexation-precipitation　systems　of　Me-OH-,　Me-OH--CO32-,　Me-OH--S2-,　Me-OH--NH3　and　Me-OH--NH3-CO32-.　The　thermodynamic　equilibriums　of　these　systems　were　studied.　The　results　show　that　Fe3+in　systems　of　Me-OH-　and　Me-OH--NH3　can　be　separated　by　precipitation　through　adjusting　the　pH　value　to　3.　However,　Co,　Ni　and　Mn　can　be　separated　only　in　Me-OH--NH3-CO32-　system.　The　theoretical　calculations　show　that　the　behavior　of　Co,　Ni　and　Mn　in　Me-OH--NH3-CO32-　system　is　affected　by　pH　value,　complexing　agent　concentration　and　precipitant　concentration.　The　increase　of　the　total　concentration　of　carbonate　[C]　is　in　favor　of　the　precipitation　of　Ni,　Co　and　Mn,　but　the　increase　of　the　total　ammonia　concentration　[N]　has　the　opposite　effect.　When　[C]=1　mol/L,　[N]=2　mol/L　and　pH　value　of　9-10,　most　Ni　is　complexed　in　the　solution　in　the　form　of　senior　ammonia　complexes　[Ni(NH3)42+]　and　[Ni(NH3)52+],　[Ni(NH3)62+],　while　Co　and　Mn　precipitate　in　MnCO3and　CoCO3.　Finally,　Co　can　be　separated　with　Mn　from　the　solution　in　Me-OH--S2-　system　when　pH