Three Gram-negative bacteria from commercial fresh fish were identified as Pseudomonas sp.,an important food spoilage bacteria, on the basis of 16S rDNA sequences.N-aeyl-homoserine lactones (AHLs) were the important quorum sensing molecules and regulated the expression of many characteristics in a cell-density-dependent manner in Gram-negative bacteria.The AHL biosensor detection revealed that three isolates produced AHLs molecules and strains FML05-1 and FML05-2 produced two types of AHLs at least and the main signal mole-cules were N-3-oxo-octanoyl-homoserine lactone (N-3-oxo-C₈-AHL).Also the amount of AHL in FML05-2 reached to the maximun at 12h throughout growth.This was first study of quorum sensing signal molecule AHLs produced by the pseudomonas from food and layed the foun-dation for new strategies of food preservation based on interfering in quorum sensing of spoilage bacteria.