The　valley　splitting　has　been　realized　in　the　graphene/Ni　heterostructure　with　the　splitting　value　of　14　meV,　and　the　obtained　valley　injecting　efficiency　from　the　heterostructure　into　graphene　was　6.18%　[Phys.　Rev.　B　92　115404　(2015)].　In　this　paper,　we　report　a　way　to　improve　the　valley　splitting　and　the　valley　injecting　efficiency　of　the　graphene/Ni　heterostructure.　By　intercalating　an　Au　monolayer　between　the　graphene　and　the　Ni,　the　split　can　be　increased　up　to　50　meV.　However,　the　valley　injecting　efficiency　is　not　improved　because　the　splitted　valley　area　of　graphene　moves　away　from　the　Fermi　level.　Then,　we　mend　the　deviation　by　covering　a　monolayer　of　Cu　on　the　graphene.　As　a　result,　the　valley　injecting　efficiency　of　the　Cu/graphene/Au/Ni　heterostructure　reaches　10%,　which　is　more　than　60%　improvement　compared　to　the　simple　graphene/Ni　heterostructure.　Then　we　theoretically　design　a　valley-injection　device　based　on　the　Cu/graphene/Au/Ni　heterostructure　and　demonstrate　that　the　valley　injection　can　be　easily　switched　solely　by　changing　the　magnetization　direction　of　Ni,　which　can　be　used　to　generate　and　control　the　valley-polarized　current.