Abstract: The polypropylene modified by rutile type nano-TiO₂ was degraded by accelerated aging test with high pressure mercury-arc lamp.The ultraviolet and visible light spectra of some samples were analyzed with ultraviolet and visible light spectrophotometer,such as nano-TiO₂,nano-TiO₂/polypropylene composites and so on.It was noted that rutile type nano-TiO₂ had excellent ultraviolet shielding function.The capacity of shielding ultraviolet was increased by 2 times when the polypropylene was filled with 0.5wt% nano-TiO₂.The shielding ultraviolet capacity of polypropylene was increased by 9 times when modified by nano-TiO₂ cooperating with hinderd amine light stabilizer(HALS).And the capacity of shielding ultraviolet had not any loss after 14 days artificial weathering,according which can endue excellent aging resistance function to modified polypropylene for long time.