The　polycarboxylate　superplasticizer/calcium　silicate　hydrate　(PCE/C-S-H)　nanocomposites　have　been　used　as　an　enhancing　agent　for　the　early　strength　development　of　cementitious　materials　by　providing　nucleation　site　for　cement　hydrates.　This　study　aims　to　investigate　the　mechanism　and　the　effect　of　PCE　on　the　microstructure　and　properties　of　C-S-H.　PCE/C-S-H　with　varying　calcium-to-silicon　ratio　(C/S)　are　prepared　via　the　co-precipitation　method　in　PCE　solution　using　methyl　ally　polyethylene　glycol　(MAPEG)　as　macromonomer　and　characterized　by　means　of　XRD,　FTIR,　TG,　DSC,　TEM,　DLS,　zeta　potential　and　TOC.　The　mortar　strength　containing　PCE/C-S-H　with　different　C/S　ratio　is　investigated　at　early　curing　age.　The　results　from　XRD　show　that　the　basal　spacing　of　C-S-H　interlayer　is　increased,　indicating　that　the　PCE　can　intercalate　into　the　interlayer　of　C-S-H,　which　is　consistent　with　the　results　from　TG　and　DSC.　Besides,　the　synthesized　C-S-H　can　be　well　protected　from　carbonation　in　the　presence　of　PCE.　Combining　the　results　of　XRD,　FTIR　and　TOC,　it　can　be　revealed　that　PCE　only　can　graft　in　the　vacant　sites　in　silicate　chain　of　C-S-H　with　C/S　ratio　of　1.7.　Zeta　potential　results　show　that　PCE　can　adsorb　the　surface　of　C-S-H.　The　results　from　mortar　compressive　strength　show　that　the　PCE/C-S-H　with　low　C/S　has　a　more　acceleration　performance　than　high　C/S　for　low　calcium　content　of　PCE/C-S-H　that　contains　more　loose　foil-like　flasks　than　higher　content　of　calcium,　which　can　provide　more　nucleation　sites　for　hydration　products.