The mixed strains from chilled pork were inoculated into the liquid medium which was packaged with different concentration of CO2. The samples were stored at 5 ℃ and the number of Pseudomonas, Enterobacteriaceae, Lactic acid bacteria and total number colonies were collected at different time during the storage. The results demonstrated that the concentration of CO2 has little influence on Lactic acid bacteria since its facultative anaerobes; CO2 concentration can effectively curb the maximal growth speed of Pseudomonas and Enterobacteriaceae; the higher the CO2 concentration, the stronger the inhibition; high CO2 concentration can curb the growth speed of total number of bacteria colony; the inhibition effect of CO2 concentration on the growth speed of Pseudomonas and Enterobacteriaceae and the growth speed of total number of bacteria colony can be described by a two-parameter equation.