Abstract: We mainly wanted to find out the relationship between leaf shape and its inner quality of flue-cured tobacco in Xuanwei county of Yunnan Province. We collected 127 flue-cured tobacco samples and measured their leaf length, width, weight, detected their main chemical components, and evaluated their smoking quality. The content of total sugar, reducing sugar, the starch, Rs/Nic TN/Nic decreased and content of total nitrogen and nicotine increased with the increase of leaf length. The content of total sugar, reducing sugar, the starch, Rs/Nic TN/Nic increased and content of total nitrogen and nicotine decreased with the decrease of leaf length-width ratio. The content of total nitrogen decreased with increase of width. The K2O content and TN/Nic reduced with increase of leaf weight. The length-width ratio of tobacco leaf had principal effect on its smoking quality, leaf width and leaf weight next. Based upon the above analyses, the authors conclude that the bigger length-width ratio was the uppermost limiting factor to smoking quality in Xuanwei county of Yunan Province.