Abstract: To investigate the comprehensive properties of medium and high ultra-high-molecular-weight polyethylene (UHMWPE) fibers, such as their resistance to ultraviolet (UV) aging, and to promote their industrial application in fields like deep-sea aquaculture or offshore fisheries, this experiment conducted artificial accelerated UV aging on medium and high UHMWPE, regular UHMWPE fibers, and low-creep UHMWPE fibers. Using scanning electron microscopy, Fourier-transform infrared spectroscopy, thermal stability tests, and mechanical tensile tests, the changes in the structure and properties of the three types of UHMWPE fibers over UV irradiation periods of 7 to 28 days were analyzed. The results show that UV irradiation causes main-chain scission in UHMWPE fibers, leading to molecular degradation, which subsequently affects their thermal stability and reduces their mechanical properties. After 7 and 14 days of UV irradiation, the knot strength of medium and high UHMWPE fibers with the linear density specifications of 1600D, 3000D, and 6000D was improved to varying degrees. With the increase of the UV irradiation period, the decrease in knot strength and elongation at break of 1600D medium and high UHMWPE fibers was smaller compared to regular UHMWPE fibers and low-creep UHMWPE fibers of the same specification. The research shows that during a 28 day UV irradiation period, medium and high UHMWPE fibers exhibited better UV aging resistance, thermal stability, flexibility, and elasticity than the other two types of UHMWPE fibers, with smaller differences in mechanical performance. The overall performance of medium and high UHMWPE fibers is close to that of regular UHMWPE fibers. This study can provide a reference for the development and application of medium and high UHMWPE fiber rope and net materials for fisheries.