The definition of fitness is the ability of bacteria to regulate their metabolism to adapt to surrounding environmental conditions for reproduction and survival, and their growth and reproduction ability, competitiveness, virulence, and so on may undergo a series of changes. At present, the detection rate of the main carbapenem resistant Enterobacteriaceae (CRE) bacteria is showing an increasing trend, and the persistence, diffusion, and fitness of the main CRE bacteria in clinical departments are closely related. This article provides a review of the research progress on the fitness mechanisms of major CRE bacteria, in order to predict the epidemic patterns of major CRE bacteria and provide reference for controlling their spread