This paper discusses CNT's applications in thermal management. High-performance heat dissipation pastes for thermal interface applications were developed by dispersing CNT powder into a silicone oil that widely used in thermal interface material, Thermal conductivities of the resulting samples were measured. The effects of loading wt% of CNT and size and geometric on the thermal conductivity and performance of paste were also investigated. The results showed that the thermal conductivity of the silicone oil enhanced to 1.640 W/mK from pure silicone oil with value 0.165 W/mK. As the loading of CNT increases to 60 wt% the thermal conductivity increase to 4.237 W/mK. The geometric that long cylindrical in shape improve the ability of CNT to enhance the thermal conductivity properties but will cause losing the conformability of paste.