Determination of the valid components in traditional Chinese medicine is one of the key steps for its identification, and the development of accurate and simple methods is necessary for the present analysis work of medicines. In this paper, the experimental conditions were optimized and procedures chosen for determination of emodin and chrysophanol by lunminol-H2O2-Cr3+ chemiluminescence quenching system. The dynamic range for determination of emodin was 10(-4)-10(-8) g/ml (r = 0.9965), with a detection limit of 1.57 x 10(-9) g/ml. The RSD and recovery for determination of 10(-7) g/ml of emodin (n = 6) were 0.4% and 92.8% +/- 0.5%, respectively. Satisfactory results were also obtained when the method was used to determine chrysophanol. This method was used, after separation by thin layer chromatography, to determine emodin and chrysophanol in several traditional Chinese patent medicines, and the results were in good agreement with those obtained by the standard colorimetric method.