Abstract: Two kinds of GNPs/PP thermally conductive composites were prepared with KNG180 GNPs or KNG150 GNPs via melt blending, and their thermal conductivity, density, crystallization behavior and thermal stability were investigated. The results show that the density of KNG180 GNPs/PP composite is higher than that of KNG150 GNPs/PP, and the crystallization degree improvement of PP is higher when filled with KNG180 than KNG150. The thermal conductivity of composites was dramatically improved along with the increase of GNPs content, and the improvement of KNG180 GNPs/PP is much higher than KNG150 GPNs/PP. The composites contained 60% mass fraction of KNG180 has a thermal conductivity of 1.32 W/(m·K) which was more than 14 times as that of the pure PP(0.087 W/(m·K)). As the GNPs incorporated, thermal stability of the GNPs/PP composites is enhanced. When the mass fraction of KNG180 and KNG150 was 10%, the maximum mass loss rate temperature is increased from 345.1 ℃ to 374.6 ℃ and 397.9 ℃, respectively. But when the contents of KNG180 or KNG150 reach to a certain content, the thermal stability begins to decrease.