[Background] Quorum sensing often causes resistance to antibiotics in Pseudomonas aeruginosa infection, so it is urgent to find new inhibitors. [Objective] To investigate the mechanism of Fermentation extract by Inonotus obliquus in Commelina communis against Pseudomonas aeruginosa targeting quorum sensing system and the reasons. [Methods] The microdilution method was adopted to determine the minimal inhibitory concentration of fermentation extract for PA; The effects of fermentation extract on Biofilm formation, pyocyanin production, LasA proteases activity and productionof rhamnolipid were detected by microtitration; Analyze chemical compounds changed by HPLC, The Folin-Ciocalteu method was used to detect Total phenolic content of FCC and UCC. [Results] The MIC of Pseudomonas aeruginosa for FCC and UCC was 16 g/L and 64 g/L, respectively; FCC could significantly inhibit the activity of Biofilm formation and Virulence factors of bacteria; The use of fermentation as separate processes could change the levels of many compounds in fermentation extract. The total phenol content of the fermented extract increased by 219.97% compared with the unfermented extract. [Conclusion] The results of present study suggested that FCC enhance inhibited Pseudomonas aeruginosa quorum sensing system function and plays a role bacteriostatic action by anti-quorum sensing activity.