Recently, zeolitic imidazolate framework-8 (ZIF-8) has been widely studied and used as a catalyst in various fields, due to its high specific surface area, tunable channels and thermal and chemical stability. In this paper, ZIF-8 was used as a precursor to fabricate a Ag/ZnO photocatalyst, and the influence of Ag on the photocatalytic activity of ZnO has been explored. All samples were characterised using XRD, SEM, TEM, and UV-vis diffuse reflectance spectra. The photocatalytic activity of all samples was evaluated by the degradation of a rhodamine B solution under UV light. The results show that ZIF-8 was completely transformed into ZnO when it was calcined at 550 °C for 6 h, and Ag was well loaded onto ZnO. The photocatalytic efficiency of ZnO is 92.32%. When ZnO was doped with Ag, its photocatalytic efficiency was highly improved (99.64%). Furthermore, Ag/ZnO exhibited high photocatalytic stability. After five repeated cycles, the photocatalytic activity of Ag/ZnO was highly retained at 97.48%.