The invention relates to a bacterial strain WXX-2 and a bacterial agent for controlling peanut root rot. The bacterial strain is Bacillus pumilus with the preservation number of CGMCC No. 11540. The 16s rRNA base sequence of the bacterial strain is shown as SEQ ID No.1. Chitinase produced by the bacterial strain and used for degrading fungal hypha cell walls has higher activity ad has significant degradation capacity against fungal pathogen hyphae such as fusarium oxysporum, fusarium solani, blight bacteria, rhizoctonia and the like infecting roots of crops. The quantity of seed dressing with the bacterial agent is generally only 10-15 kg/mu, damage by the frequent peanut root rot in upland red soil can be effectively controlled, the control effect reaches 60% or higher, and the bacterial strain WXX-2 and the bacterial agent have the advantages of small application quantity, broad antibacterial spectrum, remarkable yield increasing effect and the like, and the influence of the root rot on the loss of peanut yield is effectively reduced.