Diamond-wire sawing silicon waste (DSSW) from photovoltaic silicon wafer sawing process represents a resource worth recovery and recycling. In this contribution, in order to utilize DSSW with low cost and high value, composite Si nanostructures for photocatalytic H2 evolution were innovatively synthesized by a simple, one-pot metal-assisted chemical etching (MACE) method from DSSW. The morphologies, phase structure, elemental composition and optical properties of the composite were characterized by XPS, BET, XRD, SEM, TEM, HRTEM and UV–vis. DRS, the photocatalytic performance was evaluated by water splitting under visible light. The results indicated that a visible light responsive Ag nanoparticles/porous silicon/silicon nanosheets (AgNP@PSi/SiNS) composite was obtained. Owing to the porous and nanosheets features, the specific surface area of the composite is as high as 377.968 m2 g−1 and quantum confinement effects is successfully triggered to broaden the band gap of silicon from 1.12 eV to 1.31 eV, which allows an excellent hydrogen evolution amount of 367.65 μmol g−1 in the initial 1 h. In addition, the effect of Ag amount on the morphologies and photocatalytic performance of the composite was investigated. This study presents a promising route for the fabrication of composite silicon nanostructured photocatalysts from industrial silicon waste for solar hydrogen generation, demonstrating the potential for waste recovery and energy conversion. Display omitted •A composite Si nanostructures were fabricated from DSSW by MACE method.•The specific surface area of AgNP@PSi/SiNS achieves to 377.968 m2 g−1•The quantum confinement effect is triggered to broaden the band gap of silicon.•A H2 evolution rate of 367.65 μmol h−1g−1 under visible light was obtained.