Abstract: The modified multi-walled carbon nanotubes (MWCNTs) with different functional groups on the surface were prepared by the methods of mixed acid oxidation and surface graft reaction. The impact strength at cryogenic temperature and the coefficient of thermal expansion (CTE) values for the pure epoxy and different MWCNTs modified epoxy were studied. The results show that—NCO group terminated PEO oligomer can be introduced to the surface of MWCNTs through surface grafting reaction, which can improve the dispersion state of nanotubes and strengthen the interfacial bonding between nanotubes and epoxy matrix. In comparison to pure epoxy, impact strength at cryogenic temperature of MWCNTs, O-MWCNTs and S-MWCNTs modified epoxy composites with 0.5% mass fraction are increased 10.27%, 26.13% and 32.95%, respectively, and CTE values under T_g range are decreased 14.79%, 29.59% and 40.29%, respectively. It indicates that S-MWCNTs can improve the impact strength at cryogenic temperature and decrease the CTE values under T_g range of epoxy resins.