In order to study the stability of akebia saponin D (ASD) in biological fluids in vitro, the determination methods of ASD were established in this study. Akebia saponin D was dissolved in artificial gastric juice, intestinal juice and gastrointestinal contents of rats, respectively, then thermostatically maintained at 37 degrees C. At time intervals after degradation, samples were withdrawn and the concentrations of ASD were determined by HPLC, from which stability of it at different biological specimen was evaluated. As a result, ASD was totally degraded in large intestinal contents of rats in 8 hours. ASD was very stable in artificial gastric juice, intestinal juice and gastric contents of rats. All of the above data proved that ASD was easily degraded by coliform bacteria but stable in acid environment and with the presence of digestive enzyme.