In chemiluminescent analysis, the reaction system of luminol-hydrogen peroxide is always used under the alkaline condition, and the reaction is advantageous through the medium of catalyzing horseradish peroxidase. After being added, the enhances were found to be able to improve the sensibility of the chemiluminescence. P-tertiarg butyl phenol and P-cresol phenol appeared to be good enhancers, which can increase the emission intensity obviously at least 20 times, and effectively prolong the luminescence time. The mechanisms of the enhancers were studied in the paper. The experiments demonstrated that the key point of selecting enhancers is to form a aromatic free-radical.