Abstract：A novel method of on-line evaluation of antioxidants by capillary electrophoresis (CE) with indirect chemiluminescence (CL) detection was reported. It is based on the CL of luminol suppressed for lessened hydroxy radical which is scavenged by antioxidants in base condition. Optimal chemiluminescence conditions were obtained, and the antioxidant activities of thiourea and ephedrine were evaluated. The IC50 values of thiourea and ephedrine were obtained by fitting curves, and the order of antioxidant activity is ephedrine＞thiourea. The result was consistent with that of fluorospectrophotometry. The proposed method was preliminarily applied to evaluating the antioxidant activity of components of Sophora japonica L.