In order to expand the application of hydrothermal carbon from forestry residues in photocatalyst carrier field, the ZnO/hydrothermal carbon composite material was obtained by one-step hydrothermal synthesis method. In this method, the raw material contained hydrothermal carbon, zinc acetate and ammonia water. The composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). The photocatalytic activity and degradation kinetics of the photocatalysts were studied by the degradation of methyl blue solution. The results showed that: the ZnO/hydrothermal carbon composite material can be prepared under the experimental conditions. ZnO had a hexagonal wurtzite structure and the size of ZnO significantly reduced with the increasing content of hydrothermal carbon. However, when the quantity of hydrothermal carbon reached 24.6%, the ZnO changed from rod to sheet. The photocatalytic results indicated that the composite photocatalysts exhibited higher photocatalytic activity compared with pure ZnO, and when the content of hydrothermal carbon reached 19.7%, ZnO/hydrothermal carbon exhibited the best catalytic performance, leading to as much as 83.1% reduction of MB concentration. The reaction of photocatalytic oxidation is the first order reaction in kinetics.