AIM:To predetermine the period of efficacy of Diedahuoxue film former METHODS:The chemical stability of Diedahuoxue film former was studied by the constant temperature accelerated test according to the principle of chemical kinetics Using the emodin in Diedahuoxue film former as an index,its content was determined by spectrophotometry The period of efficacy of Diedahuoxue film former was determined RESULTS:The results showed that the decomposition of emodin in Diedahuoxue film former accorded with the primary reaction CONCLUSION:At room temperature(25℃),it is predetermined that the period of efficacy of Diedahuoxue film former is 1 10 years