A method and apparatus for power-efficiency management in a virtualized cluster system. The virtualized cluster system includes a front-end physical host and at least one back-end physical host, and each of the at least one back-end physical host comprises at least one virtual machine and a virtual machine manager. Flow characteristics of the virtualized cluster system are detected at a regular time cycle, then a power-efficiency management policy is generated for each of the at least one back-end physical host based on the detected flow characteristics, and finally the power-efficiency management policies are performed. The method can detect the real-time flow characteristics of the virtualized cluster system and make the power-efficiency management policies thereupon to control the power consumption of the system and perform admission control on the whole flow, thereby realizing optimal power saving while meeting the quality of service requirements.