To enlarge the use of PLA in the field of packaging, PLA nanocomposites are prepared by us and to better develop the effect of the silicon nanoparticle, the surface of nanoparticles are modified by introducing PLA chains via “grafting to” method. According to the results of 1H NMR and TGA, it shows that the PLA grafted Silicon nanoparticles are successfully synthesized by controlling the reaction condition and the molecular weight of the grafted PLA chains is relatively high. PLA Nanocomposites with modified nanoparticles are prepared using a convenient melt blending method to guarantee well-distribution of the particles. The well-dispersion state of silica nanospheres is confirmed by Scan Electrical Micrograph (SEM) technology. From the dynamic shear rheology tests, the strain and time sweep both reveal that stability networks are formed in these nanocomposites. And the frequency sweep shows that the nanoparticles with long grafted chains dramatically enhanced the storage and viscosity effect of the pure PLA. The rheology testing suggests that strong particle-matrix interactions between molecularly/nano-level dispersed grafted silicon and PLA chains formed and the elongational viscosity of PLA has been markedly improved with the addition of the nanoparticle. The effect of modified nanoparticles on the thermal properties of PLA has also been studied by us using DSC and in-situ FTIR technology. It reveals that the crystallization rate of PLA has been improved as the long grafted chain play as the sites of nucleation for PLA. Finally based on the rheology and crystallization researches, the nanocomposites are used to prepare PLA blowing films. Compared to pure PLA and unmodified silicon particles series, it shows that the stability of the film blowing has been greatly improved and the blow-up ratio is increased. The grafted nanoparticles holds significant candidate to use as processing agent in in the field of PLA stretch shaping process.