By the pharmacopoeia method, the water and total flavonoids contents of fresh purslane at different growth stages were analyzed. Test results showed that the water content of purslane grass, stems and leaves did not significantly decreased with the extension of growth stages. The total flavonoid content in purslane grass, stems and leaves reduced gradually with the extension of growth stages. The total flavonoid content of purslane leaves at the later growth stage was significantly higher than that in whole plant and stem. By the dynamic determination and distribution of the total flavnoids content at different growth stages, the appropriate harvest time of purslane is the mid growth stage.