Abstract: 【Objectives】 Carbon and nitrogen metabolism is affected by the activities of various enzymes,their variations directly or indirectly affect the contents and proportions of various chemical constituents of tobacco, impacting the quality of tobacco. In this paper, tobacco cultivar Yunyan 97 was used as materials, and the activity differences of some enzymes affected by the growing altitudes were investigated to provide references for high quality tobacco cultivation in Wumeng hilly area, Yunnan Province.【Methods】 Tobacco leaf samples were collected in different growing stages. The conventional chemical components of flue-cured tobacco were analyzed. The cell ultra structure was observed using transmission electronic microscope, the activity of nitrate reductase was measured using sulfa colorimetric method, and the activities of amylase and invertase by 3,5-dinitrosalicylic-acid method, the activities of sucrose synthase and sucrose phosphate synthase using conventional methods.【Results】 The sugar contents is higher, the nicotine and total nitrogen contents are at a reasonable level, and the chemical components' coordination is satisfactory in the Wumeng hilly areas. The ratio of sugar to nicotine and that of total nitrogen to nicotine in the middle altitude areas are higher than in the high and low altitudes. At the 60 th day of the transplanting, the number and size of starch particles in the leaves are significantly different among tobaccos in different altitudes. The volume and number increase of the starch particles in the middle altitude areas are significantly higher than in the high and low altitudes at the same stage. From 30 to 50 d after transplanting, the activity of invertase in the middle altitude areas is greater than in the high altitude areas, while those of sucrose synthase and amylase in the middle altitude areas are less than in the high altitude areas. Around 70 d after the transplanting, the activity of sucrose phosphate synthase in the middle altitude areas is highest and that of sucrose synthase is in the middle, and accordingly, the sugar content in the middle attitude areas is higher than in the high and low altitude areas. For the nitrogen metabolism, the nitrate reductase and glutamine synthetase activities are reduced after the first rise, the activity of glutamine synthetase in the middle altitude areas is the highest, which promotes the maturation and yellowing of tobacco, and induces high contents of nitrogen and nicotine in the middle attitude areas. During the growth of flue-cured tobacco, due to the coordination of the enzyme activities, the ratio of sugar to nicotine and the ratio of nitrogen to nicotine in the middle attitude areas are better than those in the high and low altitude areas.【Conclusions】 Altitude is an important factor to influence the carbon and nitrogen metabolism of flue-cured tobacco in Wumeng. Comparing the three altitudes, cell development of tobacco in the middle altitude areas is more reasonable, the coordination of the carbon and nitrogen metabolism is better and the chemical composition is more coordinated, and the areas can be used as predominant areas for planting tobacco in Wumeng.