γ-rays irradiation was used to graft monomers vinyltrjmethoxysilane onto polypropylene powders and then the obtained PP-g-Si was hydrolyzed to get cross-linking. In this paper, the effects of the absorbed dose on the grafting degree of the monomer vinyltrjmethoxysilan and gel content of the cross-linked samples were investigated. Adding the styrene as the second monomer can make grafting ratio up to 4.2%. The grafting ratio increases with the increment of absorbed dose, while gel content of the cross-linked samples induced by hydrolysis does not increase simultaneously. Because the irradiation can cause the molecular main-chain broken, melting flow rates (MFR) of PP-grafting-vinyltrjmethoxysilane decreases. The melting temperature of PP-g-Si has been investigated by DSC and crystal structure of PP-g-Si has also been studied by use of XRD.