Pseudomonas fluorescens is a dominant spoilage bacterium commonly found in fresh aquatic products， and its spoilage ability is regulated by a quorum -sensing system of N-homoserine lactones (AHLs). Based on the quorum-sensing quenching activity， the type of quenching activity substance from strain YF-2 was analyzed using heat inactivation and acid sensitivity tests. The results showed that strain YF-2 had a significant quenching effect on P. fluorescens AHLs， with a degradation rate of 100%. Its quenching active substance existed in the crude cell extract (CCE)， which was preliminarily identified as acyltransferase or oxidoreductase by heat inactivation and acid sensitivity assays. The degradation of C4-HSL， C6-HSL and C8-HSL treated by the CCE at protein concentrations of 20， 40 μg/mL and 80 μg/mL ranged from 52.8% to 100%， and the inhibition and clearance rate of P. fluorescens biofilms ranged from 25.84% to 56.63% and 26.12% to 59.35%， respectively. In addition， the confocal laser scanning microscopy showed that the CCE reduced the thickness of P. fluorescens biofilm and disrupted the biofilm structure. Meanwhile， Bacillus cereus was recognized as the source of strain YF-2. The application of B. cereus to control the spoilage bacterium P. fluorescens in aquatic goods will have a theoretical foundation thanks to this study.