With the development of the computer technology and network technology, the size of data collected is increasing rapidly. It is difficult to process and analyze so big data in real-time. Cloud computing is an effective tool for real-time processing for big data. How to make full use of cloud computing to analyze big data is a hot issue in recent year. Because of the limit of current network transmission speed, there is much communication between the selected cloud computing nodes during big data processing, which will cause a heavy transmission delay and lead to the reduce of real-time.