A method for migrating a virtual network function instance, wherein the method is performed by a source virtual network function, and comprises: starting a running status information replication operation, wherein the replication operation comprises: sending a copy of first running status information to a destination virtual network function, wherein the first running status information is running status information that already exists in a source virtual network function before the replication operation is started; when starting the replication operation or before starting the replication operation, starting a signaling message migration operation after receiving a first signaling message and a second signaling message, wherein the migration operation comprises: (a) before the first signaling message is processed by the source virtual network function, forwarding the first signaling message to the destination virtual network function, wherein the first signaling message is used to instruct the destination virtual network function to create second running status information on the destination virtual network function; and (b) sending a copy of the second signaling message to the destination virtual network function, wherein the copy of the second signaling message is used to instruct the destination virtual network function to update the first running status information or the second running status information; and (S103, S104) if determined that the copy of the first running status information is received by the destination virtual network function and that both the first signaling message and the copy of the second signaling message are processed by the destination virtual network function, allowing the source virtual network function to go offline, so that the destination virtual network function runs the virtual network function instance. starting a running status information replication operation, wherein the replication operation comprises: sending a copy of first running status information to a destination virtual network function, wherein the first running status information is running status information that already exists in a source virtual network function before the replication operation is started; when starting the replication operation or before starting the replication operation, starting a signaling message migration operation after receiving a first signaling message and a second signaling message, wherein the migration operation comprises: (a) before the first signaling message is processed by the source virtual network function, forwarding the first signaling message to the destination virtual network function, wherein the first signaling message is used to instruct the destination virtual network function to create second running status information on the destination virtual network function; and (b) sending a copy of the second signaling message to the destination virtual network function, wherein the copy of the second signaling message is used to instruct the destination virtual network function to update the first running status information or the second running status information; and (S103, S104) if determined that the copy of the first running status information is received by the destination virtual network function and that both the first signaling message and the copy of the second signaling message are processed by the destination virtual network function, allowing the source virtual network function to go offline, so that the destination virtual network function runs the virtual network function instance.