Virtualization technology has revolted the computer technology. In the paper, we present our virtual computer cluster. The components of computer cluster have been improved by virtualization technology from the actual computer server to virtual server instance. Virtual computer cluster includes front-end machine and the cluster nodes. The front-end machine can be physical machines or virtual machines; the cluster node can also be virtual or physical machine node. The front-end machine of the cluster communicates with the cluster nodes through physical or virtual network adapter. The front-end machine connects with the cluster management software in each node so as to monitor and control every physical or virtual node within the cluster. A single virtual computer cluster extends its resources with adding physical or virtual resources including computing resources, storage resources and etc. within secure and stabile occasions with special needs. The technology can be widely applied to cluster and parallel computing demand but with lower-cost system design scenarios.