Ultra-high molecular weight polyethylene (UHMWPE) fiber is considered as one of the high-performance fibers. However, the inert surface of UHMWPE fiber limits its application in many fields. In order to optimize the application of UHMWPE fibers in functional and composite fields, this work introduced a special surface structure of the UHMWPE fibers. The designed surface was formed by the flower-shaped ZnO (F-ZnO) crystals, which endowed the UHMWPE fibers with photocatalytic property. Moreover, F-ZnO on the UHMWPE fiber surface enhanced the roughness of the fiber, which improves the interfacial bonding strength of fiber-reinforced composites. The experimental results showed that the surface wettability of the F-ZnO-UHMWPE fibers was improved significantly. Moreover, F-ZnO-UHMWPE fibers were used as immobilized photocatalyst, and the degradation rate of rodamine B reached 53.3 %. F-ZnO-UHMWPE fiber also could be used in fiber-reinforced composites fields. Compared with the pure rigid polyurethane (RPU) and UHMWPE fibers/RPU composites, the tensile strengths of F-ZnO-UHMWPE fibers/RPU composites were improved by 130.3 % and 44.2 % respectively.