The chemical stability of aqueous solution of ferulic acid was studied by the constant temperature accelerated test according to the princiPle of chemical dynamics. The ferulic acid in sample was determined by HPLC. The result showed that the decomposition of ferulic acid in aqueous solution accords with the primary reaction. At room temperature (25℃),the time of decomposition of 10℃ ferulic acid in aqueous solution (the expiry date of drug) was calculated robe 19. 36mo and 17.41 too-20. 69mo,calculated by classical and simple calculation methods, respectively.