In this work, we aimed to develop a novel method for the target preparation of multicomponent composites Au@CdS/g-C3N4 towards high visible light photocatalytic activity with the assistance of L-cysteine biomolecules. Through the interaction of L-cysteine biomolecules with Au nanoparticles and g-C3N4 bulks, CdS layer were in-situ precipitated on the surface of Au nanoparticles to form core-shell structure Au@CdS and Z-scheme structure Au@CdS-g-C3N4 with good interface bonding in composites. By taking advantage of this feature, the highest reaction rate constant of 8%Au@CdS/g-C3N4 for methyl orange dye and phenol degradation was 3.08- and 1.48-folds higher than pure g-C3N4 bulks, which was ascribed to the strong interaction between different substances for efficient charges transferring and separation as evidenced by the studies of X-ray photoelectron spectroscopy, steady-state and transient photoluminescence spectroscopy. This work highlights the utilization of biomolecules for the target preparation of composites and its application on environmental remediation.