A data flow migration method and device are disclosed. When migration between a source virtual machine and a target virtual machine is started, determining a silent time used for processing data flow migration; and receiving, within the silent time, a data flow packet sent by a switching node; and sending the data flow packet to the target virtual machine according to the data flow packet and a data flow migration policy. In this way, the silent time is used, a newly arrived data flow is redirected, and the newly arrived data flow is directly sent to the target virtual machine according to the data flow migration policy, which avoids migration of the newly arrived data flow. Therefore, data flows that arrive at the source virtual machine are on the decrease, and system migration performance is effectively improved.