Abstract: The study was focused on the leaf age regulation of Gynostemma pentaphyllum(Thunb)Makino. The results show that there was an apparent positive correlation between the increase of leaf age and the content of saponins. And harvesting dates of G.pentaphyllum is after 400-leaf age. Using of this exterior index can carry through science management to the plant of G.pentaphyllum, which method is simple and easy to do, and have effective practical value to actual production