Keywords: 
• Morinda citrifolia Linn. /
• total flavonoids /
• dynamic changes /
• ultraviolet spectrophotometry

Abstract: Ultraviolet spectrophotometry was used to study the dynamic changes of total flavonoids in vegetative organs of Noni（ Morinda citrifolia Linn.） at different growth stages in a view to determine the appropriate time and organs for harvesting. This method was good in repeatability and high in precision to determine the total flavonoids in Noni. The recovery rate was 99. 66% and the testing result was reliable. The flavonoids content of Noni in different organs varied in the order of 90 days old leaves ＞ 270 days old leaves ＞ 30 days old leaves ＞hairy roots ＞ 210 days old leaves ＞ 150 days old leaves ＞ lateral roots ＞ 330 days old leaves ＞ taproots ＞twigs ＞ old branches ＞ biennial branches ＞ perennial branches ＞ annual branches. This indicated that Noni leaves were the priority organ for extraction of total flavonoids in Noni. Considering the plant growth and leaf utilization,it is best to select 270 days old leaves of Noni as the medicinal material to extract total flavonoids.