To scale up and down the resource usage of stake holders such as customers, the cloud computing environment is used. In this paper, we present a system that uses virtualization technology to allocate data center resources dynamically based on application demands, the green computing is supported by optimizing the number of servers in use. We introduce the concept of “skewness” to measure the unevenness in the multidimensional resource utilization of a server. By minimizing skewness, we can combine different types of workloads nicely and improve the overall utilization of server resources. We develop a set of heuristics that prevent overload in the system effectively while saving energy used. Trace driven simulation and experiment results demonstrate that our algorithm achieves good performance.