Secondary　magnesium　battery　is　a　green　battery　which　is　expected　to　be　applied　in　electric　vehicles.　It　has　more　advantages　than　lithium　ion　battery.　The　main　components　of　a　secondary　magnesium　battery　are　Mg　anode,　electrolyte　solutions　and　Mg2+　intercalation　cathode　materials.　To　our　present　knowledge,　only　the　solutions　of　derivatives　of　Grignard　reagent　RMgX　in　ether　could　be　employed　as　the　electrolyte.　Among　that　few　intercalation　positive　materials　of　Co3O4,　V2O5　and　Mo3O4,　Mo3O4　is　the　best.　The　electrochemistry　of　Mg　anode　is　controlled　by　the　complicated　absorption　processes,　and　the　nature　of　adsorbed　species　depends　primarily　on　the　electrolyte　used.　The　cycling　efficiency　of　Mg　electrodes　is　determined　by　the　morphology　of　the　Mg　deposits.　By　improving　the　electrolyte,　e.g.　with　mixed　solvent,　mixed　electrolyte　and　supporting　electrolyte　used,　and　in　creasing　the　size　of　anion,　or　by　improving　the　intercalation　cathode　with　doping,　the　performance　of　rechargeable　magnesium　battery　could　be　made　better.