In order to investigate the relationship between main nutrient elements and aroma precursors of flue－cured tobacco，taking cv. K326 with liquid-based cultivation as material，changes in contents of major aroma precursors such as plastid pigments (chlorophyll，lutein，β-carotene) and polyphenols (chlorogenic acid，rutin) systematically in growing process of flue-cured tobacco under N，P，K，Mg deficiency condition were figured out. The results indicated that deficiency of major nutrient elements would seriously affect the main aroma precursors. N，K，P，Mg deficiency would extremely inhibit formation of plastid pigments and polyphenols anabolin，N deficiency affected carotenoid the most，P，Mg deficiency followed，K deficiency once again followed，and P deficiency affected polyphenols the most，Mg，K deficiency followed，N deficiency affected the least. Therefore，mainatining an adequate and reasonable supply of N，P，K，Mg in the latter period of production and having a further study on balanced fertilization are vital to improve the aroma and quality of flue-cured tobacco in China.