Five types of modification reactions were used to introduce PE chains onto the surface of nano SiO2 and reactive nano SiO2, where silanol groups were chlorinated using tetrachlorosilane (SiCI4). The results show that the reaction between Si Cl and the epoxy group is more active than the others, and the highest grafting ratio is up to 41.4% deduced from,the thermogravimetric analysis (TGA). The result of TEM and SEM indicate that the PE-modified SiO2 particles are uniformly dispersed, and the SiO2 particle size is approximately 100-300 nm. The shear rheology results reveal that the PE chains covalently attached on the surface of the nanosilica have strong interaction with the PE matrix and enhance the melt strength of LDPE. The thermal properties of LDPE/SiO2 nanocomposites almost remain unchanged via TGA and differential scanning calorimetry (DSC) experiments.