The Z-Scheme heterojunction is extremely attractive in the field of photocatalysis to solve the electron-hole separation transport path because of its unique bi-photon system that can efficiently improve the photocatalytic rate. In this study, the hydrothermal method was used to in situ synthesize two-dimensional/two-dimensional (2D/2D) WO₃/Ag:ZnIn₂S₄ Z-Scheme heterojunction composites. Meanwhile, the microstructure, phase structure, chemical environment and optoelectronic properties of 2D/2D WO₃/Ag:ZnIn₂S₄ Z-Scheme heterojunction composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflection spectroscopy (UV-Vis DRS), photoelectrochemical (PEC), and photoluminescence (PL) spectra, respectively. Furthermore, under visible light irradiation (using a filter with λ>420 nm), the performance of 2D/2D WO₃/Ag:ZnIn₂S₄ Z-Scheme heterojunction composites for hydrogen production and photodegradation of methyl orange (MO) was assessed. The results show that the photocatalytic performance is also significantly enhanced with the addition of Ag:ZnIn₂S₄ content, in the 2D/2D WO₃/Ag:ZnIn₂S₄ Z-Scheme heterojunction composites. When the mass fraction of Ag:ZnIn₂S₄ was 35.0%, it showed the best hydrogen production rate (158.93 μmol.g_-1^.h_-1^{) and degradation rate (0.18 min_-1}). This work provides new insights into design and construction of Z-scheme heterojunction based on WO₃ nanosheets for visible light catalytic hydrogen production and pollutant degradation.