To investigate the evolution characteristics of the interface strength of geosynthetics, a large-scale ultraviolet (UV) aging model test chamber was used to conduct aging tests on geomembrane (GMX) and geotextile (GT) for up to 80 days and 40 days, respectively. Periodically collected aged specimens were utilized to perform temperature-controlled direct shear tests on GMX-sand, GT-sand, and GMX-GT interfaces. The influence of UV aging on the shear strength of these three interfaces was quantitatively analyzed. The results show that UV aging has a stronger effect on the shear strength of the GMX interface than on the GT interface. Furthermore, the shear strength of the aged GMX-GT interface exhibits a trend of initial increase followed by a decrease with prolonged UV aging time.