A strain of Bacillus cereus D8 isolated from raw milk with high enzyme activity in protease production was taken as the research object. The relationship between AI-2 and protease was clarified by adding signal molecule AI-2 and changing the culture conditions of the strain (temperature， pH， osmotic pressure， nutritional conditions)， and the correlation between the production of AI-2 and protease activity of the strain was explored. The concentration of signal molecule AI-2 and the activity of protease in supernatant were detected by HPLC and azo casein method. The results showed that the concentration of AI-2 was positively correlated with the activity of protease at different temperature， pH and osmotic pressure. Under hypotrophic stress， Bacillus cereus could induce more signal molecule AI-2， and the protease activity of Bacillus cereus decreased， and the two were negatively correlated. Conclusion: Different culture conditions affect the production of signal molecule AI-2 and the activity of protease， and there is correlation between the two.