Abstract: Effects of water conditions on the main chemical components of flue-cured tobacco variety “G80’’under potculturing were studied．The results show that the total sugar，K and nicotine contents of the middle and superior leaves decreaSe and the total N and protein contents increase．reaching very significant levels by flooding treatments．The two changing tendencies increase with the increase of the treatment levels．The total sugar，nicotine and total N contents of the middle and superior leaves rise，K and protein contents decline very significantly，but there are no significant differences in the main chemical components of the middle leaves between root extension period and mature period by drying treat-merits．