Abstract: A new chemiluminescence （CL） system gold nanorods-luminol-AgNO3 was built and gold nanorods were found to exhibit higher catalytic activity towards luminol CL than gold nanospheres. CL spectra, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX) were used to characterize this system. The effects of various reaction conditions, the morphology and protection reagents of nanoparticles on the CL reaction were also investigated. The mechanism of the CL reaction was proposed. Finally a novel microplate-compatible chemiluminescence immunoassay based on this new CL system was developed for the determination of human immunoglobulin G (IgG) with a linear range from 25 to 1 000 μg/L and a detection limit of 153 μg/L.