Abstract: In order to solve the problem of new flue-cured tobacco varieties to promote the process of fertilization, taking ‘Yunyan 97’ as experimental material, Field trials were conducted to investigate the effects of nitrogen fertilizer and ratio of N to K on flue-cured tobacco chemical quality. The results indicated that, effects of nitrogen rate, ratio N to K, and their interaction on tobacco chemical compositions, chemical harmony indices and chemical harmony score were up to significant levels. With the nitrogen rate increased, tobacco chemical harmony score(CHS) increased first then decreased. With the ratio of N to K decreased, tobacco chemical harmony score (CHS) increased. In all these treatments, treatment of nitrogen rate 180 kg/hm2, and ratio of N to K reached 1:3 was of best comprehensive chemical quality, followed by the treatment of nitrogen 180 kg/hm2, ratio of N to K reached 1:2.5. In Chaling County, to obtain get tobacco with good chemical quality, to be N 180 kg/hm2 was recommended with a ratio of N to K of 1:(2.5-3).