Objective To explore the effect of heating temperature and heating time on the dissolution characteristics of phenolic acids in water extract of Danshen Decoction. Methods The contents of tanshinol, protocatechuic aldehyde and salvianolic acid B in water extract of Danshen Decoction were determined by reverse-phase high performance liquid chromatography (RP-HPLC) . The changes of the contents were monitored by classic constant temperature acceleration method. Results Of the three components, the content of salvianolic acid was decreased with the increase of heating temperature and the prolongation of heating time, and the degradation characteristics of the salvianolic acid B met the first-order kinetics equation. Conclusion The water-soluble components have less stability in the water extracts of Danshen Decoction. Lignum Santali Albi and Fructus Amomi accelerate the degradation speed of Radix Salviae Miltiorrhizae, suggesting that we should pay attention to the influence of heating temperature and heating time on the content of salvianolic acid B in the extraction and concentration process.