In order to make full use of the resource of SDN controllers, as well as to improve the load balance degree among those controllers, a dynamic switch migration mechanism is proposed in this paper. The proposed dynamic migration solution is designed based on the Self-Optimizing Mechanism (SOM). It divides the network into several domains according to the deployment of SDN controllers. By comparing the relevant parameters of each domain, the proposed mechanism can quickly select appropriate target switches and migrating destinations. The load balance of multi-controller, flow latency and algorithm complexity are the main factors of the algorithm. The advantage of the algorithm is that it can flexibly manage the SDN control plane by local dynamic adjustment. Simulation results verify that the proposed mechanism can enhance the balance among controllers, and reduce the flow setup latency, while the computation complexity during the migrating process is kept at a reasonable level.