Abstract: When wood-plastic composites are used as outdoor building decoration materials, they are exposed to ultraviolet light, resulting in mechanical properties and service life reducing. The rutile nano TiO₂ with high-efficiency ultraviolet shielding ability was surface-modified with a silane coupling agent KH-570, and then TiO₂-WF/PP composites were prepared with wood fiber (WF), polypropylene (PP). The artificial accelerated UV aging of the composites was carried out. The effects of nano TiO₂ on the UV aging of WF/PP composites were investigated by means of FTIR, TG, SEM, mechanical properties analysis and color change analysis. The results show that the modified nano TiO₂ particles can be uniformly dispersed in WF/PP composites without obvious agglomeration, and their addition significantly improves the thermal stability of the composites; with the aging time prolonged, the decrease of the mechanical properties of WF/PP composites is relatively small and the color change scope is small. When the mass fraction of nano TiO₂ particles is 2 wt%-3 wt% and aging for 2 000 h, the tensile strength and impact strength of the TiO₂-WF/PP composites only decrease by 10.0% and 12.6%, respectively, while those without the addition of nano TiO₂ particles decrease by 20.2% and 22.6%, respectively.