A novel CuSZnS1−xOx/g-C3N4 nanocomposites were prepared by a thermal decomposition process and a hydrothermal method. The effects of the Cu(NO3)2 dopant precursor concentration and weight ratio of g-C3N4/ZnS1−xOx on the morphology, crystalline properties, optical property, photocurrent were investigated by using the field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectra (DRS), photocurrent response, and hydrogen production tests. Decorating CuS improved the absorption of the heterostructured photocatalysts. H2 production rate was increased from 9200 to 10,900 μmol h−1 g−1 by incorporating CuS. By loading 5 wt% g-C3N4 on CuSZnS1−xOx, the maximal hydrogen production rate of the composite catalyst reached 12,200 μmol g−1h−1 under UV light irradiation. Introducing g-C3N4 helps to separate photogenerated electron–hole pairs. After being operated for 3 cycles, the recycled CuSZnS1−xOx/g-C3N4 photocatalyst retained 87% of its original activity.