Taking　advantage　of　simultaneous　thermochemical　lithiation　and　densification　of　spark　plasma　sintering,　the　Li21Si5/graphene　nanocomposites　with　uniform　distribution　and　high　density　were　prepared.　Due　to　the　two-dimensional　structure　and　excellent　electrical　conductivity　of　graphene,　and　the　presence　of　a　high　proportion　of　tightly　bonded　interfaces　of　Li21Si5/graphene,　the　volume　shrinkage　of　the　active　particles　during　the　delithiation　process　was　limited　effectively,　and　the　charge　transport　inside　the　active　particles　was　enhanced　dramatically.　Therefore,　the　composite　exhibits　excellent　electrochemical　performance.　The　specific　capacities　of　pre-delithiation　and　the　first　lithiation　were　968　mAh.g(-1)　and　1007　mAh.g(-1),　respectively,　which　are　3　times　as　high　as　those　of　the　commercial　lithium-carbon　compound.　Its　first　Coulomb　efficiency　was　94.5%　at　the　same　time.　Moreover,　the　specific　capacity　remained　590　mAh.g(-1)　after　100　cycles,　and　the　cyclic　stability　doubled　compared　to　the　composites　prepared　by　carbon　particles.　Even　at　a　high　current　density　of　1　A.g(-1),　the　specific　capacity　can　be　maintained　at　540　mAh.g(-1).　This　work　provides　a　new　approach　for　the　development　of　lithium-rich　alloy　anode　materials,　which　are　promising　in　high　energy　density　batteries,　such　as　lithium　ion-sulfur　and　lithium　ion-oxygen　systems.