Abstract: To investigate the composition characters of humus in tobacco growing soil and their relationships with the main chemical components in tobacco leaves, the contents and composition proportion of humus in 210 cultivated soil samples collected from 14 tobacco growing counties and the main chemical components in corresponding C3F and B2F tobacco leaves were determined, the relationships of composition characters of humus with soil types, soil pH and alkali-hydrolysable nitrogen contents were analyzed, and the effects of contents and composition proportion of humus on the main chemical components in tobacco leaves were investigated by correlation analysis. The results showed that:1) The carbon content (TC) in humus ranged from 10 to 20 g/kg. Humic acid (HA), fulvic acid (FA) and humin (HM) accounted for 11.05%-32.15%, 12.00%-36.28%, 38.43%-68.23% of total humus, respectively. HA/FA ratios ranged from 0.35 to 1.87. 2) The soil types in order of TC in humus were paddy soil> purple soil> red soil> brown soil> cinnamon soil. The humification degree was the highest in paddy soil, while the lowest in red soil. With the increase of pH, the TC in humus and its compositions decreased. Alkali-hydrolyzable nitrogen content in soil positively correlated to a certain extent with the TC in humus and its compositions and humification degree. 3) The TC in each humus constituent was significantly positively correlated with the contents of nicotine in tobacco leaves, while significantly negativly correlated with starch, reducing sugar content and nitrogen/nicotine ratio. For B2F leaves, HA/FA was significantly positively correlated with the nicotine content in tobacco leaves, while significantly negativly correlated with nitrogen/nicotine ratio.