[Background] Due to the extensive use of antibiotics, antimicrobial resistance has become a big problem. Searching for new antibacterial drugs has become a research hotspot. [Objective] Cloning and expression of quorum quenching enzyme and investigate its effect on the pathogenicity of Pseudomonas aeruginosa. [Methods] Quorum quenching enzyme gene aiiA gene from quorum quenching bacterium Bacillus sp. QSI-1 was amplified by PCR methods. The aiiA gene was cloned into the expression vector pET30a and transformed into E. coli BL21(DE3). The expression AiiA protein was purified with a HiTrap Q Sepharose column. P. aeruginosa PAO1 was cultured in medium containing different concentration of quorum-quenching enzyme. The supernatant was used to detect the level of pyocyanin, rhamnolipid and total protease, and biofilm also been detected. The quorum-quenching enzyme was applied to Caenorhabditis elegans infected with P. aeruginosa, the survival rate of the nematode was calculated. [Results] We successfully cloned an N-acylhomoserine lactonase gene from Bacillus sp. QSI-1. The purified quorumquenching enzyme significantly inhibited the production of virulence factors and biofilm formation in P. aeruginosa and reduced the mortality of nematodes infected by P. aeruginosa. [Conclusion] As a substance that can effectively inhibit pathogenic bacteria, quorumquenching enzyme may become a new drug for clinical treatment of bacterial infections.