Virtual server consolidation is to use virtual machines to encapsulate applications which are running on multiple physical servers in the cluster and then integrate them into a small number of servers. Nowadays, with the expanding of enterprise-class data centers, virtual server consolidation can reduce large number of servers to help the enterprises reduce hardware and operating costs significantly and improve server utilization greatly. In this paper, we propose the VSCM manager for virtual cluster, which solves the problems in the consolidation from a globally optimal view and also takes migration overhead into account. Experiment results in virtual cluster demonstrate that, VSCM can greatly reduce the number of servers and the migration overhead.