Disclosed a chemiluminescence enhancer and a chemiluminescence immunodetection kit. The chemiluminescence enhancer is specifically a betaine and can be used for enhancing the luminance of a luminescent acridine substance. The chemiluminescence immunodetection kit comprising the chemiluminescence enhancer and a luminescent acridine substance features greatly enhanced luminescence signals and high detection sensibility, and can be widely applied to fields such as clinical diagnoses, scientific research, and sanitation analysis.