Abstract: In order to investigate the differences of soil microbial population and tobacco leaf aroma quality at different humic acid application rates,field experiments were carried out at humic acid rates of 0,60,120 and 180 kg/hm²,the microbial population in soil and the net photosynthetic rate,aroma components,sensory quality and economic characteristics of tobacco leaves were compared.The results showed that with the increase of humic acid rate,the population of actinomycosis in soil increased significantly,while that of bacterium and fungi did not change significantly;the net photosynthetic rate,carotenoid catabolites,aromat amino acid catabolites,aroma quality,yield and output value of tobacco leaves raised,and Maillard reaction products and total aroma components increased significantly.The population of actinomycosis in soil and the aroma quality of tobacco leaves were higher,and net income was the highest at the humic acid rate of 120 kg/hm².