A novel method for the determination of methimazole was proposed,based on its enhancement effect on the luminol-silver nitrate-gold nanoparticles(AuNPs) chemiluminescence(CL) system in alkaline medium.The experimental conditions were studied.Under the optimal experimental conditions,methimazole could be detected in 3 sectional linear ranges of 1.0×10-9-1.0×10-8,1.0×10-8-1.0×10-7,1.0×10-7-1.0×10-6 g/mL with a detection limit of 3.0×10-10g/mL,and relative standard deviation was 1.2%(n=11,ρ=1.0×10-8 g/mL).The method was successfully applied in the determination of methimazole in pharmaceutical formulations.In addition,the mechanism of gold nanoparticles-luminol-AgNO3 system was also explored by the CL spectrum.