We prepared thermally reduced graphene oxide (TRG) grafted with polymethyl methacrylate (PMMA) and polyvinyl acetate (PVAc) (TRG-g-PMMA and TRG-g-PVAc) by 纬-ray irradiation-induced graft polymerization and studied their effects on poly( l -lactic acid) (PLLA) nanocomposites. PMMA and PVAc chains were proved to be grafted on the TRG surface successfully. TRG- g -PMMA and TRG- g -PVAc was found to restrict the crystallization behavior of PLLA compared with TRG. Moreover, tensile-test results showed that TRG- g -PMMA and TRG- g -PVAc could enhance the elongation at break of PLLA nanocomposites without reducing the tensile strength and modulus compared with TRG, which indicated that the grafting of PMMA and PVAc chains on TRG could improve the toughness of PLLA nanocomposites.