Correlation analysis between main chemical constituents of tobacco leaves and endogenous harmful components in mainstream cigarette smoke was conducted. Leaf stalk positions exhibited a high relation with endogenous harmful components and hazard index (H). Upper stalk position leaves had greater release of 1-butanone,4-(methylnitrosoamino)-1-(3-pyridinyl) (NNK), B\[a\]P. HCN, NH₃ and phenol in mainstream cigarette smoke, and a higher hazard index than middle position leaves except for crotonaldehyde, which had greater release from middle position leaves. Different endogenous harmful components in mainstream cigarette smoke presented complicated correlation with main chemical constituents in tobacco. The same type of leaf chemical constituents presented different correlations with various endogenous harmful components in mainstream cigarette smoke. Cigarette hazard index showed significantly positive correlations with contents of nicotine, protein, total nitrogen, major polyphenols and organic acids, while significantly negative correlation with potassium and carbonaceous substances, such as total sugars, reducing sugars and starch. The results suggested that properly increasing potassium content and decreasing nitrogenous constituents in cured tobacco leaf may reduce the cigarette hazard index.