Abstract: In order to clarify the effects of combined application of microbial fertilizers and high-carbon base fertilizers on the microbial population and soil fertility of tobacco growing soil, with cv. ZY 100 as the test material, a field experiment with 5 treatments (CK: Conventional fertilization of 52.5 kg/ha pure nitrogen; T1:1 500 kg/ha high-carbon base fertilizer; T2:1 500 kg/ha high-carbon base fertilizer + 75 kg/ha microbial fertilizer + 45 kg/ha pure nitrogen; T3:1 500 kg/ha high-carbon base fertilizer + 150 kg/ha microbialfertilizer + 37.5 kg/ha pure nitrogen; T4:1 500 kg/ha high-carbon base fertilizer + 225 kg/ha microbial fertilizer + 30 kg/ha pure nitrogen) was conducted. The results showed that: 1) The combined treatments significantly increased the microbial population in tobacco growing soil. On the 75th day after transplanting, the bacterial population in the soil reached its peak with the rank of T2>T3>T1>T4>CK. On the 60th day after transplanting, the fungal population in the soil reached its peak with the rank of T4>T3>T1>T2>CK. On the 90th day after transplanting, the actinomycetic population in the soil reached its peak with the rank of T4>T3>CK>T2>T1. 2) The combined fertilizers increased the contents (mass fraction) of alkali-hydrolyzed nitrogen, available phosphorus, available potassium and organic matters in tobacco planting soil, and improved the soil pH. Among them, T4 treatment was found to be superior in soil fertility improvement. 3) The combined application of fertilizers promoted the enzyme activities of urease and catalase in soil, and the soil enzyme activity of T4 was the highest. The combined treatments increased the soil microbial population, improved soil fertility and enzyme activity, and provided a good soil environment for the growth of flue-cured tobacco. Among all the treatments, 1 500 kg/ha high-carbon base fertilizer + 225 kg/ha microbial fertilizer + 30 kg/ha pure nitrogen had the best effect on improving tobacco growing soil.