Chemiluminescence (CL) emission can be generated by mixing potassium permanganate with captopril under acidic conditions. Formaldehyde can significantly enhance the CL signal. This phenomenon has been utilized to design a new flow-injection chemiluminescence method for the determination of captopril with the permanganate-formaldehyde-captopril CL system. Under the optimum experimental conditions, the proposed method has a quantitation linear range of captopril between 0.02 and 2.0μg mL-1, with a detection limit of 0.01μg mL-1 and a correlation coefficient of 0.9998. The method was applied to the determination of captopril in pharmaceutical preparations and the results were satisfactory.