[Background] Clubroot, one of the most important soil-borne diseases in the world, is posing a serious threat to the vegetable farming in the Northwest of Hubei, leading to an incidence rate as high as 60% for Chinese cabbage in many fields. [Objective] To study the effects of Streptomyces alfalfae XY25T application on physicochemical properties and microbial community in rhizosphere soil. [Methods] Pot experiments of Chinese cabbage were done in greenhouse, using the diseased soil with S. alfalfae XY25T application as the treatment group and the diseased soil without S. alfalfae XY25T application as the control group. On day 7, 14, 21, 28 and 35 after seedling transplantation, soil samples were collected for analysis of the variations in the enzyme activity and nutrient content in the rhizosphere soil. On day 35, the total DNA was extracted from soil samples. The composition and diversity of bacterial and fungal communities were investigated by using high-throughput sequencing technology combined with bioinformatics analysis. [Results] Compared with the control, the application of S. alfalfae XY25T increased pH value, content of organic matter, alkali-hydrolysable nitrogen, available kalium, and available phosphorus in the soil by 10.0%, 13.7%, 12.0%, 41.1%, and 8.71%, respectively. It also increased the soil enzyme activity, with an increase of 333%, 204%, and 36.1%, 142% in the soil invertase activity, urease activity, catalase activity, and alkaline phosphatase activity. Moreover, S. alfalfae XY25T application improved the soil microbial community structure and diversity, leading to an increase of 54.1%, 22.8%, and 10.7% in the relative abundance of Ascomycota, Zygomycota, and Actinobacteria, in contrast to a 7.59% decrease in the relative abundance of Acidobacteria. Furthermore, S. alfalfae XY25T application also increased the relative abundance of Penicillium, Mortierella, Mucor, and Streptomyces by 25.5%, 14.6%, 8.20%, and 7.24%, respectively. [Conclusion] The application of S. alfalfae XY25T not only improved the soil quality but also significantly altered the microbial community structure and diversity in rhizosphere soil.