The invention relates to a biological agent against crucifer club root and application thereof, belonging to the technical field of bio-pesticide. The strain for production is Bacillus subtilis XF-1, whose preserving number is CGMCC NO.2357. The stain has the characteristics as follows: (1) the primary colony on the LB culture substrate is white and round having a wet surface; the later colony is light yellow having uneven edge with dry and crimple surface; observed from the microscope, the strain is short-bar shaped and movable with spore, peritricha and dimension of 0.7 - 0.8 * 2.0-2.4 mum; (2) the strain is Gram-positive and aerobic and makes use of glycogen, sugar, citrate, gelatin hydrolysate, starch and casein, but does not make use of cellulose, tyrosine and catalase positive; (3) the stain has the function of sterilization, disease prevention, and yield improvement. The embodiment of the invention is as follows: using the test tube of Bacillus subtilis XF-1 stain, shake cultivation, and culture solution for fermentation to prepare biological agent, then applying the biological agent to the rhizosphere soil of crucifer crops, thereby having good effect in preventing and treating, and simple production.