As raw materials, expanded graphite (EG) sheets were prepared from natural graphite via intercalation-reduction method , while thermally reduced graphene sheets (T-rGO) and chemical reduced grapheme sheets (C-rGO) were prepared from graphene oxide (GO), which was synthesized by Hummers method. Then composites of polypropylene (PP)/graphite sheets were prepared with graphite sheets as fillers and PP as matrix by melt-blending method to produce composites of PP/EG, PP/T-rGO and PP/C-rGO respectively with different filler contents. The structure and properties of the three prepared composites of PP/graphite sheets are characterized by means of X-ray diffractormeter (XRD) , scanning electron microscope (SEM), thermal analysis (DSC), thermal gravimetric analysis (TGA), as well as tensile and impact tests. The results show that the tensile strength of composites of PP/EG and PP/T-rGO with 0.1% of EG or T-rGO, can reach 32.2 MPa and 33.5 MPa, which increased by 7.2% and 11.2%, respectively in comparison with that of the pure PP, while the impact strength of PP/EG and PP/T-rGO composites was improved by 27.4% and 19.6%. The tensile strength and impact strength of the composite PP/C-rGO with 0.3% C-rGO were 37.26 MPa and 37.26 kJ/m², respectively, which increased by 23.9% and 27%, in comparison with those of the pure PP. The melting temperatures, crystalline temperatures and crystalline degree of PP/graphite sheet composites were higher than those of the pure PP. In contrast to the pure PP, the melting temperature and crystalline degree of PP/C-rGO composites with 0.1% C-rGO increased 10.2^oC and 4.2%, respectively. It can be attributed to the "heterogeneous nucleation effect" of graphite sheets, which can induce the regular arrangement of PP molecular chains. The maximum decomposition temperatures of PP/EG, PP/T-rGO and PP/C-rGO composites with 0.1% of graphite sheet showed 13.5 ^oC, 9.1 ^oC and 6.9 ^oC respectively higher than that of the pure PP, indicating that the thermal stability of the composites can be improved by adding a small amount of graphite sheets. The fillers have been dispersed homogeneous in the matrix, but agglomeration appeared when excessive fillers were added.