This work presents an exploratory study of monitoring the transformation process of salvianolic acid A (SAA) using an online UV spectroscopic analysis system. A chemometrics approach, based on multivariate curve resolution of spectrophotometric matrix, was applied to resolve the concentration and spectra profiles of reactant species and to evaluate the kinetic profile. Kinetic runs have been developed at temperatures ranging from 25 to 90 àand pH values ranging from 2.5 to 10 in order to investigate the effects of these two variables during the transformation process of SAA. The degradation reaction of SAA was considered as first-order and the degradation kinetic constant of SAA increases when temperature increases. It was also found that SAA transforms rapidly when pH is higher than 7, but remains stable when pH is lower than 6.5. Two transformation products were auxiliarily identified by direct mass spectrometric analysis using Mass Work software. Our results suggest that the manufacturing process of Chinese medicine preparations with SAA as the main bioactive compound should not be operated at high temperature and high pH.