The invention discloses a lactobacillus bulgaricus strain with quorum sensing and application of the lactobacillus bulgaricus strain. The lactobacillus delbrueckii subsp. bulgaricus ljj-6 strain provided by the invention has a collection registration number of CGMCC NO. 11346, and is called ljj-6 for short. The invention further discloses a method for preparing a yogurt product. The method comprises the following steps: inoculating lactobacillus ljj-6 to liquid milk, and fermenting, so as to obtain the yogurt product. According to the lactobacillus ljj-6 provided by the invention, the flora density can be regulated in an autolysis manner in the later fermentation stage, so that the postacidification phenomenon of the yogurt is reduced, and the lactobacillus ljj-6 can serve as a high-quality yogurt fermentation agent and has major application and popularization values.