In this study, Ag or Al-doped TiO2/ZnO heterostructure nanocatalysts were prepared using a sol-gel method for photocatalysis to evaluate the degradability. The photocatalytic behavior was evaluated by the degradation of methylene blue (MB) under ultraviolet (UV) light irradiation. Photocatalytic studies suggested that 1 mol% Agdoped TiO2/ZnO (TiO2/ZnO = 0.75/0.25) heterostructure nanocatalysts showed higher photocatalytic activity, and that the degradation efficiency can reach 83% in 4 h, 14% higher than that for pure TiO2. Finally, the photocatalysis mechanism for the Ag-doped TiO2/ZnO heterostructure nanocatalysts is discussed.