Abstract: UO₂ composite fuel pellets doped with 5%-20% multi-walled carbon nanotubes (MWNTs) were prepared by hot-press and pressureless sintering processes, and their properties were studied. The results show that MWNTs are uniformly mixed into the UO₂ matrix by alcohol ball milling; the density of hot-press sintered UO₂ pellet decreases with increase of MWNTs content, the density of UO₂-5%MWNTs pellet is 96.7%TD; the density of pressureless sintered UO₂ pellet first increases then decreases with increase of MWNTs content, and the maximum density of UO₂-12.5%MWNTs is 97.2%TD. MWNTs and UO₂ do not react at 1400 ℃, 50 MPa hot-press sintering process, but a little reaction and UC phase are found at 1 750 ℃ pressureless sintering process. SEM shows that MWNTs distributes in UO₂ matrix as intergranular and transgranular. At 250 ℃, the thermal conductivity of UO₂-10%MWNTs pellet by hot-press sintering is 6.76 W/（m•K）, increased by 20.28%; the thermal conductivity of UO₂-12.5%MWNTs pellet by pressureless sintering is 6.65 W/（m•K）, increased by 18.33%.