Abstract: By Bacillus subtilis Xi-55 against Ustilaginoidea virens, its antagonistic activity was tested in vitro. Its inhibition rate, deformation effect, and effect on spore germination of Xi-55 with strong antagonistic effect and its growth-promoting effect on rice were studied. The results showed that the average inhibition rate of the metabolites of Xi-55 against U.virens was 54.64%. The average inhibition rate against spore germination of U.virens was 69.33%, while the growth-promoting effect on rice of Xi-55 was opposite.