The　efficiency　of　a　stock　market　is　principally　measured　by　its　Information　efficiency　and　functionality　efficiency.　Both　metrics　are　closely　related　to　the　information　of　stock　markets.　However,　there　is　no　uniform　definition　of　information　in　the　economy　field　since　researchers　may　have　various　opinions　on　the　information　of　stock　markets.　In　this　research,　a　comparatively　strict　definition　of　information　in　sense　of　economy　is　presented.　Based　on　this　definition,　the　optimal　conditions　to　reach　the　maximum　information　efficiency　and　functionality　efficiency　of　stock　markets　are　derived.　The　conclusion　is,　only　when　the　market＇s　operation　and　information　transmission　mechanisms　are　fully　effective,　its　information　completeness　degree　is　optimal,　all　investors　take　optimal　equilibrium　actions,　and　the　information　efficiency　and　functionality　efficiency　of　stock　markets　will　be　optimal.　Based　on　the　conclusions,　the　information　efficiency　and　functionality　efficiency　of　reality　stock　markets　in　China　are　studied　and　the　corresponding　supervision　counter-measures　are　suggested.