In this work, the effects of degradation time, temperature, and pH value on the degradation of Salvianolic acid B in aqueous solution were determined. Higher pH values, higher extraction temperature, and longer extraction time led tomore degradation of Salvianolic acid B. Danshensu concentration increased as Salvianolic acid B degraded. A mechanism model was developed considering the degradation of Salvianolic acid E and lithospermic acid, which were two degradation products of Salvianolic acid B. The reverse reactions of Salvianolic acid B degradation were also considered. Degradation kinetic constants were calibrated. The degradation kinetics of Salvianolic acid B, lithospermic acid, and Danshensu in a Salvia miltiorrhiza extract aqueous solution were predicted using the mechanism model. The predicted concentrations agreed well with the experimental results. This model was developed using degradation data obtained from simple composition systems, but it can be applied in a complex botanical mixture with high prediction accuracy. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.