Objective: In this study, Pseudomonas aeruginosa （PA） was used as the indicator bacteria, and based on the quorum sensing system, the lactic acid bacteria （LAB） that antagonized the effect of PA were screened and the antagonistic mechanism was preliminarily discussed. Methods: The mechanism of LAB antagonizing PA was explored by the tests of Oxford Cup Method screening LAB to inhibit the growth of PA, AI-2 expression of LAB, biofilm formation ability of PA, pyocyanin expression and the AI-2 expression of PA with LAB sterile supernatants, and the analysis of Pearson correlation. Results: The results showed that Lactobacillus gasseri LGchen and Lactobacillus salivarius S-5-6 have stronger abilities of antagonizing PA growth. The inhibition zone was more than 20 mm, and the relative fluorescence value of AI-2 was more than 1.2, and the inhibition rate of PA pyocyanin expression was above 50%, and the inhibition rate of PA biofilm formation was about 70%. The ability of LAB to inhibit the growth of PA was positively correlated with the ability of LAB to express AI-2 and the inhibition biofilm formation ability of PA, and this was negatively correlated with the pyocyanin expression of PA. Conclusion: LAB can inhibit the growth of PA by increasing the expression of AI-2, inhibiting PA biofilm formation and pyocyanin expression.