In order to investigate the correlation between equilibrium moisture content and some chemical components in flue-cured tobacco leaves, the chemical components in 50 representative samples of flue-cured tobacco leaf from different areas and their equilibrium moisture contents under different temperatures and relative humidities were tested. The principal component regression analysis of chemical components versus equilibrium moisture content was conducted. The results showed that: 1) Total sugar or reducing sugar is the key factor influencing the equilibrium moisture content of flue-cured tobacco leaf; 2) The equilibrium moisture content of flue-cured tobacco leaf under given temperature and relative humidity is predictable by some of the leaf’s chemical components.