Reduced graphene oxide (rGO) with various surface structures was prepared by reducing graphene oxide (GO) with hydrazine hydrate (N 2 H 4 ), sodium borohydride (NaBH 4 ) and L-ascorbic acid, respectively. The resulting rGO were used to fabricate rGO/polypropylene (PP) nanocomposites by a melt-blending method. The surface structure of rGO as well as multifunctional properties of rGO/PP nanocomposites were thoroughly investigated. It was shown that rGO with highest C/O ratio could be obtained by reducing GO with N 2 H 4 . The crystallization behaviors, tensile strength, thermal conductivity and thermal stability of rGO/PP nanocomposites were significantly improved with the increase of C/O ratio of rGO. For example, with only 1 phr (parts per hundred PP) rGO reduced by N 2 H 4 , the degree of crystallinity, tensile strength, maximum heat decomposition temperature and thermal conductivity of PP nanocomposite were increased by 6.2%, 20.5%, 48.0 ∘ C and 54.5%, respectively, compared with those of pure PP. Moreover, the thermal degradation kinetics indicated that the decomposition activation energy of rGO/PP nanocomposites could be enhanced by adding rGO with higher C/O ratio.