The concept of directly using imidazolium salts (IMSs) as mild reducing and antioxidative reagents was proposed and investigated. A simple and robust protocol for the synthesis stable, ultrafine gold nanoparticles has been established using IMSs under mild IMSs showed remarkably lower toxicity but greater antioxidative power than N-acetyl-L-cystein and (-)-epigallocatechin gallate on HSC-T6 cells. These studies demonstrate that the simple and inexpensive IMSs represent a new type of antioxidant with potential biomedical applications.