The hexamethylene diisocyanate (HDI) contained polyurethane (PU) grafted multi-walled carbon nanotubes (HDI-g-MWNTs) have been synthesized by simple blending method to fabricate thermal conductive nanocomposite. This method shows that HDI-g-MWNTs can improve the interfacial compatibility between HDI-g-MWNTs and matrix. The HDI base PU thermal conductive film (HDI-PU) showed enhanced dispersibility of functionalized MWNTs because of low crystallinity which was affected by its steric hindrance. The length of MWNTs was prevented until the end of the reaction. The long distance of MWNTs could be help to make good thermal conducting path. These phenomena have influence on the excellent thermal conductivity. The thermal conductivity increased from κ=0.274 W/mK to κ=0.645 W/mK, as the addition of the MWNTs increase to 1.2 vol%. The interconnectivities of HDI-Polyurethane have higher value than other composite films.