Abstract: The application of organic fertilizer has a great impact on the soil rhizosphere ecological area. In order to study the effects of a mixed organic fertilizer (peat, sesame cake, humic acid and mineral fertilizer) on the flue-cured tobacco rhizosphere, a potted plant experiment was conduced to investigate the effects of application rates of the mixed organic fertilizer on root vigor of flue-cured tobacco, soil enzyme activities and soil microbial biomass. The results showed that:(1) Application of the mixed organic fertilizer at the rate of 500 g per plant showed the greatest improvement of flue-cured tobacco root vigor, and it enhanced the root vigor of fluecured tobacco by up to 200.06% 60 days after transplanting. (2) The activities of soil urease, invertase and catalase were increased most significantly at the application rate of 500 g per plant, and 60 days after transplanting the enzyme activities were increased by 53.45%, 33.98% and 61.90%, respectively. Application of the mixed organic fertilizer at 750 g per plant had the most obvious effect on soil microbial biomass carbon, followed by the application rate of 500 g per plant. At the time of 60 days after transplanting these two application rates improved the contents of soil microbial biomass carbon by 97.51% and 82.04% respectively. (3) The flue-cured tobacco root vigor, soil enzyme activities and soil microbial biomass carbon all showed a peak 60 d after transplanting for all the treatments, suggesting that application of the mixed organic fertilizer can significantly enhance root vigor, soil enzyme activities and soil microbial biomass carbon, and that the appropriate application rate is 500 g/plant for the purpose of improving rhizosphere soils of flue-cured tobacco.