How　the　multi-walled　carbon　nanotubes　(MWCNTs)　influenced　the　Young＇s　modulus　of　C-S-H　was　investigated　at　multi-scale　in　this　paper.　The　functionalized　MWCNTs　dispersed　by　ultrasonication　were　mixed　with　CaO　and　nanosilica　to　prepare　MWCNTs/C-S-H　composites　with　calcium　to　silicon　ratios　(C/SD)　of　1.5　and　2.0　respectively,　and　the　contents　of　MWCNTs　were　1%　and　3%　of　the　total　mass　of　CaO　and　nanosilica.　The　Young＇s　modulus　of　MWCNTs/C-S-H　was　evaluated　by　atomic　force　microscope　(AFM)　at　multi-scale.　The　effect　mechanism　of　MWCNTs　on　Young＇s　modulus　of　C-S-H　was　analyzed　by　various　testing　techniques　and　homogenization　method.　The　BSE,　TEM　and　N-2　adsorption　tests　results　showed　that　MWCNTs　acted　as　a　bridge　to　reduce　the　number　of　cracks　caused　by　shrinkage　of　C-S-H.　Meanwhile,　MWCNTs　can　reduce　the　porosity　of　C-S-H　by　filling　the　pores.　The　AFM　consequence　illustrated　that　Young＇s　modulus　of　C-S-H　was　increased　by　MWCNTs　at　both　nano　and　micro　scales.　At　the　nano　scale,　MWCNTs　increased　the　Young＇s　modulus　of　C-S-H　by　increasing　the　mean　chain　length　(MCL)　of　C-S-H.　At　the　micro　scale,　MWCNTs　increased　the　Young＇s　modulus　of　C-S-H　by　increasing　the　Young＇s　modulus　of　C-S-H　globules　and　reducing　the　porosity　and　the　amount　of　cracks.