AIM: To study the best harvest time of Isatis Indigotica Fort.. METHODS: The adenosine content was determined by HPLC, and at the same time, the dry substance accumulation, the alcohol extract of the herb were also compared at the different growth periods of Isatis indigotica Fort.. RESULTS:During its whole growth period, the contents of adenosine and alcohol extract increase and very fast before November. The dry substance accumulates highly in December. CONCLUSION: In consideration of the yield and the contents of adenosine and alcohol extrat, the best harvest time should be between November and December.