Abstract: The hybrid of polyethyleneimine-decorated fullrene (C₆₀−PEI) was synthesized by the addition reaction between active −NH− bonds in PEI and C=C bonds in C₆₀ , and the molecular structure and morphology of C₆₀−PEI were characterized by FTIR and TEM. The C₆₀−PEI/polypropylene (PP) composite was prepared through the melt blending method and its thermal and flame retarded properties were studied. The thermogravimetric analysis results show that the thermal stability of the C₆₀-PEI/PP composite is significantly higher than the C₆₀/PP composite, because C₆₀−PEI can play the radical capture role of C₆₀ more effectively. The oxidation induced test (OIT) results show that the C₆₀−PEI/PP composite has higher anti-oxidative ability than the C₆₀/PP composite; the micro-calorimeter results also show that the heat release of the C₆₀−PEI/PP composite is obviously lower than the C₆₀/PP composite.