Abstract: The effect of different agronomic measures namely No topping(T1),Topping(T2),Topping+ K2SO4(T3),Topping + applying IAA 1 time(T4),Topping + K2SO4+ applying IAA 1 time(T5),and Topping + K2SO4 + applying IAA 2 times(T6) on NR and POD activities,potassium and nicotine content in flue-cured tobacco leaf was studied in this paper.The results showed that T6 had the highest NR and POD activities,and T1 had the lowest NR and POD activities in mature leaf.With the time after topping,K content for different treatments decreased stepwise with lowest magnitude for TI and T6 and highest magnitude for T2.The order of potassium content(%) at mature leaf for different treatments was T1(3.59)T6(2.77)T5(2.47) T3(2.11) T4(2.10)T2(1.88).On the contrary,content of nicotine for different treatments increased stepwise with time after topping,and the order of nicotine content(%)at mature period was T2(3.53) T3(3.03) T4(2.92) T5(2.70) T6(2.45) T1(1.18).At field period,potassium content had highly significant negative correlation with nicotine content(r=-0.938,P0.01),and highly significant positive correlation NR and POD activity with correlation coefficients of 0.838and 0.859 respectively(P0.01).After flue-curing,the chemical components of cured leaf for T6 were well coordinated with a suitable content of nicotine, lower content of starch,and highest content of potassium and total sugar.Applying both IAA and K2SO4 in the topping day could increase potassium and decrease nicotine in flue-cured tobacco leaf.