The　effect　and　the　interaction　mechanism　of　functionalized　multi-walled　carbon　nanotubes　(MWCNTs)　on　C-S-H　gel　were　studied　in　this　paper.　Fourier　infrared　spectroscopy,　acid-base　titration,　Raman　spectroscopy　and　transmission　electron　microscopy　were　utilized　to　analyze　the　pristine　MWCNTs　and　functionalized　MWCNTs,　showing　that　the　degree　of　graphitization　of　the　functionalized　MWCNTs　reduced.　And　the　surface　of　the　functionalized　MWCNTs　was　grafted　with　acidic　functions　which　the　content　was　2.5　x　10(-3)　mol/g.　Afterward,　the　MWCNTs/C-S-H　composite　was　prepared　by　well-dispersing　the　functionalized　MWCNTs　and　the　C-S-H.　The　experimental　results　showed　that　for　the　C-S-H　produced　with　different　designed　molar　ratios　of　CaO　to　nano-silica　(C/S-D),　the　measured　molar　ratio　of　Ca　to　Si　(C/S-M)　of　the　C-S-H　decreased　and　the　interlayer　spacing　of　the　C-S-H　increased　with　the　increase　of　the　amount　of　the　functionalized　MWCNTs.　When　C/S-D　=　0.8,　the　polymerization　degree　of　the　C-S-H　decreased　and　the　proportion　of　the　capillary　pores　increased　gradually　with　increasing　the　amount　of　the　functionalized　MWCNTs.　When　the　values　of　C/S-D　were　1.5　and　2.0,　the　trends　the　polymerization　degree　and　the　proportion　of　the　capillary　pores　of　C-S-H　were　opposite　to　those　of　C/S-D　=　0.8.　The　reasons　were　further　analyzed　based　upon　the　above　experimental　results.