Abstract: The present paper is concerned with the application of dual wavelength spectrophotometry to the determination of indigo and indirubin in Oingdai (Isatis indigotica Fort.) without preliminary separation. Satisfactory results were obtained. The average recovery of indigo was 99.62～100.7% with CV<2.80%, that of indirubin was 99.74～100.9% with CV<2.39%. Five batches of samples were determined, the results were compared with those obtained by the method of Chinese Pharmacopoeia (1977). The method described is simple, rapid and accurate.