PP/PE/TiO2 composite fibers were prepared by melt blending of polyethylene (PE), polypropylene (PP) and titanium dioxide nanoparticles (TiO2).The effects of TiO2 content on the structure, dynamic and mechanical properties of the composite fibers and photocatalytic degradation properties were investigated.The results show that TiO2 is uniformly dispersed in the composite fiber matrix as micro-aggregates, and the aggregate size increases with the increase of TiO2 content. The addition of TiO2 has no significant effect on the melting temperature (Tm) of the composite fibers, and a small amount of TiO2 has the effect of promoting nucleation, increasing the crystallization rate and increasing the crystallinity. With the increase of TiO2 content, the breaking strength and Knoting strength of the composite fibers first increased and then decreased, and a small amount of TiO2 had the effect of strengthening and toughening the composite fibers.After photodegradation for 200h, the breaking strength of the composite fibers, the nodule strength loss rate and the TiO2 content tended to be linear. With the increase of TiO2 content, the mechanical properties of the composite fibers decreased significantly, the breaking strength and Knoting strength loss rate increased significantly, and the photodegradation performance was enhanced.