Today's Internet mobility management is facing great challenges to satisfy the requirement of scalability and flexibility, such as heavy signaling overhead, data traffic centralization, etc. In this paper, some mobility management design principles concerning the trend of large-scale and high-density wireless network are given. A mobility management scheme is proposed according to these principles by taking advantage of the separated control plane and flexible programmability in software defined network. In this scheme the switches lying in the core of the network are stateless. Flow rules in the core switches are not correlated with the mobile hosts in the network, which simplifies the flow rules in the core switches sharply. The implementation on a real SDN testbed shows that this scheme gets less cost and more efficient than other solutions based on SDN.