In this work, a simple hydrothermal method was used to prepare a series of ZnO/r-GO (ZGO-x) catalysts. The obtained products were subjected to a series of characterizations, which showed that the zinc oxide particles were deposited onto r-GO and that the crystal structure was not disrupted. In addition, due to the large specific surface area and the good electrical conductivity of r-GO, more photogenerated electrons can be rapidly transferred from ZnO to r-GO to participate in the reaction, thus improving the photocatalytic performance. The degradation rate of the ZGO-3 sample reached 100% for RhB after simulated sunlight irradiation for 150 min, whereas the pure ZnO degraded RhB by about 83% under the same environment. ZGO-3 also showed the best photocatalytic degradation of methyl orange, with 100% degradation in 180 min, whereas pure ZnO degraded only 87.64% of methyl orange under solar irradiation.