Abstract: Based on the fact that Ag nanoparticles could enhance the chemiluminescence (CL) intensity of the system of luminol-potassium ferricyanide-daidzein system-sodium hydroxide, a flow injection chemiluminescence method was developed for the determination of daidzein. Under the optimum conditions, a linear relationship was found between the CL intensity and the mass concentration of daidzein in the range of 5.0×10-5-1.0×10-2g·L-1 with the detection limit (3S/N) of 6.5×10-6g·L-1. Recovery rates obtained by standard addition method were in the range of 96.2%-104%, with RSDs (n=3) less than 3%.