Objective: Lactobacillus plantarum RX-8 is isolated from traditional Chinese pickles. This strain has the excellent characteristics of producing IIb bacteriocin Plantaricin EF， but the yield is low. At present， co-cultivation with exogenous microorganisms is often used to increase the production of bacteriocin， but the specific regulatory mechanism in the co-cultivation system is still unclear. Therefore， in this study， by knocking out plnA of the intraspecific quorum sensing signal molecule， a co-culture system with lack of intraspecific quorum sensing was constructed to explore the regulation mechanism of the interspecific quorum sensing system on bacteriocin synthesis. Methods: A gene deletion mutant strain Lactobacillus plantarum ΔRX-8 was constructed， and the difference in growth， the secretion of signaling molecules and the expression of related genes between the mutant strain and the wild strain with Bacillus subtilis 1.8715 during the co-cultivation process， and analyzed the regulation of the induction system for bacteriocin synthesis. Results: After knocking out the key gene plnA， the growth curve of the mutant strain in co-culture was not significantly different from that of the wild strain， but the production of bacteriocin was decreased. Compared with mono-culture， the secretion of the quorum sensing signalling molecule AI-2 in the co-culture system was significantly increased in the early stage， and then converged to the same level， with no significant difference at the strain level. In the mon-culture system， the expression of plnBCD gene in the two-component system of the mutant strain was slightly lower than that of the wild strain， and the expression of the bacteriocin synthesis gene plnEF also decreased. The expression levels of the genes LuxS and pfs， which regulate the synthesis of the interspecific signaling molecule AI-2， were not affected by the knockout. Conclusion: In the co-culture system lacking of intraspecific signal molecules， the interspecific quorum sensing system can still make effects， and there may be a phenomenon of sharing a two-component system， which jointly regulates the synthesis of bacteriocin.