Virtualization technology, being the most effective solution to the resource management of cloud computing, excels in it is virtual machine real-time migration technology. One key issue of live migration of virtual machine is how to quickly and transparently migrate virtual machines to meet Service Level Agreements (S LAs). In this paper an improved time-series based precopy approach technique is proposed. With the time-series prediction technique, frequently updated dirty pages (high dirty pages) are identified more precisely, and transmit them in the last round of iteration, in order to reduce unnecessary, repeated transmission of dirty pages. Doing so can significantly reduce the total migration time.