Abstract: In order to identify the effects of potassium (K) fertilization regulation on quality and output in fluecured tobacco leaves， a field experiment was conducted to study the top dressing stage of K fertilizer on the general chemical compositions， mineral elements， petroleum ether extracts， neutral aroma constituents and economic characters in middle and upper leaves of tobacco (Nicotiana tabacum) cv. Zhongyan 100. The results showed that the output was increased when the top dressing stage of K fertilizer was at rosette stage， faster growing stage， maturing stage (T4) respectively， or at faster growing stage and maturing stage (T5， T2， T3). As well as the contents of potassium， phosphorus in middle and upper leaves， petroleum ether extracts， neutral aroma constituents， aroma products degraded from carotenoid， and Maillard reaction products of upper leaves were increased. However， the contents of reducing and total sugar were decreased. Besides， the contents of calcium， magnesium and copper were regulated under different top dressing stages of K fertilizer. So it is very important to hold the top dressing stage of K fertilizer for improving potassium and aroma constituents in tobacco leaves， and the T4 was the best treatment measure．

Key words: potassium fertilization, top dressing periods, fluecured tobacco, yield, quality