Green cloud computing aims at reducing the cost of cloud services in the premise of guaranteeing the quality of service(QoS). To solve this problem, we make a trade-off between migration performance and energy consumption. The basic idea of this paper is to concentrate workloads into a minimum set of nodes and close the idle ones to save energy. At the same time, we consider the performance of Virtual Machine migration to guarantee the QoS. The experiment result shows that this strategy can reduce the number of open node and give consideration to migration energy consumption and migration delay. So it guarantees the QoS in the premise of saving energy.