Phenolic compounds are secondary metabolites often implicated in plant-microorganism interactions. However, how these compounds would affect the growth of both pathogen and antagonists is not yet fully understood. In this study, the two main phenolic acids (benzoic acid and 3-phenylpropanoic acid) were screened and identified by ultra-performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS), and their contents in tobacco root exudates were evaluated. Furthermore, their effects on the biomass and activity of rhizosphere microorganisms, especially the bacterial wilt pathogen Ralstonia solanacearum and its antagonist Brevibacillus brevis in both liquid culture and soil were investigated. The results showed that the concentrations of benzoic acid and 3-phenylpropanoic acid were 0.25Ī¼ggā1 and 1.15Ī¼ggā1 dry roots, respectively. Both of them could promote the growth of the pathogen and antagonist at low concentration (benzoic acid ā¤2Ī¼gLā1 and 3-phenylpropanoic acid ā¤3Ī¼gLā1), while at high concentration, the growth of bacteria was inhibited. The minimum suppressed concentrations of these phenolic acids for R. solanacearum were higher than that for the antagonist. The growth of pathogen and antagonist together with the rhizo-microbial functional diversity significantly reduced by adding 4Ī¼gkgā1 benzoic acid or 8Ī¼gkgā1 3-phenylpropanoic acid in the soil. In conclusion, pathogen adapted better to the accumulation of tobacco root exudates than antagonist, which might be the cause of tobacco bacterial wilt outbreak in mono-cropping system.