Abstract: Objective To observe the growth characteristics of clpP mutant strains of Streptococcus mutants and to compare the growth difference of standard strains and clpP mutant strains under oxidative stress. Methods The standard strains and mutant strains were cultured respectively in TPY medium and TPY medium containing H2O2 with the terminal concentration of 0.0005% under microaerophili condition at 37℃. After inoculated in the mediums, the growth curve of each stain was determined and compared by Thermo Labsystems at an interval of 2 hours under 600nm. Results ①Growth cycle of the mutant strains changed in TPY medium.The exponential phase was ahead of time and the mutant strains grew faster than standard strains (P＜0.05).The peak value in exponential phase and A value in stationary phase of standard strains were higher than those of mutant strains(P＜0.05). ②Both strains grew slower in TPY medium containing H2O2. Conclusion Inactivation of clpP gene can reduce the capacity of Streptococcu mutans to grow and to resist oxidative stress.