This study introduces Au nanoparticles into ZnIn 2 S 4 through electrodeposition to overcome the limitation of rapid charge carrier recombination on the photoelectrochemical efficiency. The strong coupling of Au nanoparticles with the FTO substrate not only serves as an electron acceptor but also exhibits a surface plasmon resonance (SPR) effect, significantly enhancing charge carrier separation efficiency. Experimental results demonstrate that the introduction of Au nanoparticles notably improves the light absorption capability of ZnIn 2 S 4 , enhancing its solar energy conversion efficiency and rendering it an effective photoelectrocatalytic catalyst. Electrochemical analysis shows that the modified sample achieves a photocurrent density of 0.52 mA/ cm 2 at 1.23 V (vs RHE), which is 2.15 times that of pure ZnIn 2 S 4 , validating the potential of this approach for photoelectrocatalytic applications.