Abstract: Using the data of national purchase tobaccos and supervision of leaf grade quality during industry/commerce hand-over tobaccos, the maximum theoretical and practical values of the high-class-leaf percentage (HCLP) of flue cured tobacco were estimated by the leaf number and weight per leaf of individual plant. The result showed that the ultimate theoretical value of the HCLP of flue cured tobacco in perfect condition was 60% based on the leaf number of individual plant. On account of the weight per leaf, the ultimate theoretical value of HCLP was 69.3%, whereas the practical value was 30.1% for the worldwide average value, less than 45% for the maximum value and about 10% for the minimum value in tobacco-growing district, less than 40% for the actual value in majority of the provinces. The HCLP was increased to some degree after different modes of optimizing structure in the field by removing top (T) and bottom (B) leaves which were inapplicable in the cigarette formula. The actual value of HCLP on the base of weight per leaf was 33.5% averagely in the mode of removing 1 top leaf and 2 bottom leaves ("T1B2" for short, similarly hereinafter), reaching its highest level 49.6% in tobacco-growing provinces; 35.2% averagely in "T2B2" mode, reaching its highest level 52.2%; 37.2% averagely in "T3B2" mode, reaching its highest level 55.1%; 38.5% averagely in "T2B2" mode, running up to its highest level 57.1%, below 50% about this actual in majority of the provinces. It was concluded that the modes of optimizing structure have limitation in the increase of HCLP. Various ways should be adopted to resolve the imbalance between supply and demand of tobacco leaf in structure