The effects of graphene nano-platelets (GNPs) content on melt flow behavior and flexural properties of reinforced polypropylene (PP) composites were investigated. The results showed that both the flexural modulus and strength at room temperature increased when GNPs weight fraction was lower than 0.4 wt.%, and then decreased with increasing GNPs weight fraction. During the melt flow of the PP composites in capillary extrusion within temperatures ranging from 180 to 230 degrees C and in apparent shear rates varying from 100 to 4000 s(-1), the melt shear flow followed the power law relationship, and the dependence of the melt shear viscosity on temperature obeyed the Arrhenius equation. The correlation between the melt shear viscosity and GNPs weight fraction was approximately linear under the given test conditions.