Abstract: This study aimed to determine the optimal time to harvest Mesona chinesis Benth.Polysaccharide and flavonoids contents of the herb were measured using a spectrophotometer.The changes on the contents and yield of M.chinesis Benth showed the best time for the harvest seemed to be during the last 10days in August, when the polysaccharide content was 1.96%, flavonoids, 13.83% and the yield, 240 gram per plant.