Abstract: A field experiment was conducted to investigate the effect of combining application of various potassium (K) fertilizers on plastid pigment, some enzyme activities in carbon-nitrogen metabolism and quality in flue-cured tobacco (cv. zhongyan 100 ). The results showed that, compared to common K fertilizer, slow release K fertilizer improved the carbon metabolism in all growth stages of flue-cured tobacco and the nitrogen metabolism in maturity stage. common K fertilizer + slow release K fertilizer treatment and common K fertilizer + slow release K fertilizer + fulvic acid K treatment improved the contents of plastid pigment and the level of carbon-nitrogen metabolism. However, the contents of chl and activity of nitrate reductase in flue-cured tobacco leaves with treatment of common K fertilizer + slow release K fertilizer was still high in maturity stage, which impeded the nitrogen metabolism transform into carbon metabolism timely and the tobacco leaves mature normally. The treatment common K fertilizer + slow release K fertilizer + fulvic acid K not only improved the contents of plastid pigment and the level of carbon-nitrogen metabolism in early growth stages of flue-cured tobacco leaves, but also promoted the nitrogen metabolism transform into carbon metabolism timely and the tobacco leaves mature normally. Overall, the slow release K fertilizer and the combined application of other K fertilizer significantly improved the potassium content, ratio of potassium to chlorine and ratio of reducing sugar to total sugar in cured tobacco leaves. The chemical composition in cured tobacco leaves tended to be more harmonious, while total aroma constituents except neophytadiene and many different kinds of aroma constituents increased. Besides, the neophytadiene and total aroma constituents in the treatment with common K fertilizer + slow release K fertilizer + fulvic acid K also improved. Therefore this treatment was proposed as the best treatment for high quality tobacco leaves.