Clubroot caused by is one of the most destructive diseases in cruciferous crops. XY25 , a biological control agent, exhibited great ability to relieve clubroot disease, regulate rhizosphere bacterial and fungal communities in Chinese cabbage, and promote its growth in greenhouse. Therefore, field experiments were carried out to investigate the effects of XY25 on clubroot and rhizosphere microbial community in Chinese cabbage. Results showed that the control efficiency of clubroot by XY25 was 69.4%. Applying the agent can alleviate soil acidification; increase the contents of soil organic matter, available nitrogen, available phosphorus, and available potassium; and enhance activities of invertase, urease, catalase, and alkaline phosphatase. During Chinese cabbage growth, bacterial diversity decreased first and then increased, and fungal diversity decreased gradually after inoculation with XY25 . High-throughput sequencing analysis showed that the main bacterial phyla were Proteobacteria, Bacteroidetes, Acidobacteria, and Planctomycetes, and the major fungal phyla were Ascomycota and Basidiomycota in rhizosphere soil. The dominant bacterial genera were , , , , , , and with no significant difference in abundance, and the major fungal genera were , , , , , , , , and . The significant differences were observed among , , , two strains attributed to , and another two unidentified fungi by using XY25 . Moreover, quantitative real-time PCR results indicated that content was significantly decreased after the agent inoculation. In conclusion, XY25 can affect rhizosphere microbial communities; therefore, applying the agent is an effective approach to reduce the damage caused by clubroot.