In this study, an efficient catalyst Ag@g-C₃N₄ nanocomposite was successfully synthesized through a simple green reaction, and the characterizations through XRD, FTIR, SEM, BET and XPS were also studied. The activities of Ag@g-C₃N₄ were investigated toward the reduction of 4-nitrophenol to their corresponding aminophenol compounds in the presence of excess NaBH₄ as a reducing agent. The Ag@g-C₃N₄ nanocomposites exhibited high catalytic activities, in which a 92.2% 4-nitrophenol conversion in 10 min and the apparent rate constant K_app = 264.27×10^-3 min^-1 were obtained. The as-prepared Ag@g-C₃N₄ nanocomposites showed great potential in catalytically inducing the reduction of 4-nitrophenol, which makes them economically and energy conservation attractive from industrial waste water treatment.