In this work, polypropylene (PP)/reduced graphene oxide (RGO) with various surface structures were fabricated. The crystallization behaviors and non-isothermal crystallization kinetics of PP/RGO nanocomposites were thoroughly studied. The results showed that the crystallization peak temperature, crystallization rate as well as crystallization degree of PP/RGO nanocomposites were greatly enhanced with the increase of reduced extent of RGO. Non-isothermal crystallization kinetics displayed that RGO with high reduction extent exhibited strong nucleation ability, which could decrease crystallization activation energy and accelerate the crystallization process. The rheological behaviors of the PP/RGO nanocomposites were also investigated. It was found that the non-newtonian behaviors of PP nanocomposites became stronger with the increase of reduction extent of RGO.