Abstract: Four groups of different carbon and CeO2 content of ultrafine WC-9Ni-0.4Cr3C2 cemented carbide samples were prepared by powder metallurgy method. The thermal properties of the alloys were measured and analyzed using thermal constant Hot Disk analyzer through transient plane heat source method (TPS) technology; meanwhile, the phase composition and different surface morphology of the alloys after sintering were also studied by XRD, SEM and EDX analysis. The results show that, with the CeO2 content increase, the thermal conductivity and thermal diffusion coefficient of the alloy decrease, while the heat capacity increases in smaller extent. When carbon content in the WC-9Ni-0.4Cr3C2-CeO2 is low, Ce tends to gather in the alloys’ surface in the form of sulfide and oxide. With the increasing of carbon content, the gathered phenomenon of Ce in the alloy’s surface is gradually disappearing, and the thermal conductivity and thermal diffusion coefficient rise obviously. However, the specific heat capacity changes a little.