A sensitive silver nanoparticles (Ag NPs) enhanced chemiluminescence (CL) method is reported for the determination of mandelic acid (MA). This method is based on the luminol-KIO4 system catalyzed by Ag NPs to produce CL spectra. Prepared Ag NPs were characterized by UV-visible spectra and TEM image. Under optimal condition, CL spectra of the system were responded linearly with the concentration of MA in the range of 2.5×10^(-9) to 2.0×10^(-8) mol L^(-1)(r=0.9989) with a detection limit of 1.2×10^(-10) mol L^(-1). The relative standard deviation of 1.0×10^(-7) mol L^(-1) MA was found 1.45 (n=9).