To improve the dispersion of silica in polypropylene(PP) matrix and to avoid physical loss of the antioxidants, nanosilica with dendric polyamidoamines on the surface(SG-PAMAM) was synthesized by using divergent method. Then nanosilica-immobilized antioxidant(SG-PAMAM-AO) was prepared by grafting 2,6-di-tert-butyl-4-aminophenol which was derived from 2,6-di-tert-butyl-4-phenol(AO). The SG-PAMAM-AO was added into PP by melt mixing to study the aging property. The oxidation induction time of PP/SG-PAMAM-AO and PP/AO compounds was measured. It was found that the antioxidant property of the SG-PAMAM-AO was superior to that of AO. According to the changes of carbonyl absorption before and after photo-thermal aging, the photo-thermal oxidative stability of PP/SG-PAMAM-AO was much higher than that of PP, PP/SG-PAMAM and PP/AO. To improve the dispersion of silica in polypropylene (PP) matrix and to avoid physical loss of the antioxidants, nanosilica with dendric polyamidoamines on the surface (SG-PAMAM) was synthesized by using a divergent method. Then nanosilica-immobilized antioxidant (SG- AO) was prepared by grafting 2,6-di-tert-butyl-4-aminophenol which was derived from 2,6-di-tert-butyl- The was oxidation induction time of PP / SG-PAMAM-AO and PP / AO compounds was measured. It was found that the antioxidant property of the SG-PAMAM-AO was superior to that of AO. According to the changes of carbonyl absorption before and after photo-thermal aging, the photo-thermal oxidative stability of PP / SG-PAMAM-AO was much higher than that of PP, PP / SG-PAMAM and PP / AO.