The design of the mobility management is the key issue in the next-generation mobile networks. It is important to provide seamless service switching for a Mobile Station (MS) or a Mobile Node (MN) with uninterrupted services during an IP-based session between different access networks, where IP convergence has led to the co-existence of several IP-based wireless access technologies and the emergence of next generation technologies. Many recent research results of cross-layer design in mobility aim to minimize the data loss rate and delay time during switching so that users do not experience obvious and unacceptable interruptions during the handoff. The cross-layer design is the important approach for mobility management. This chapter mainly introduces and reviews existing protocols and then discusses the possible interest and useful applications of cross-layer in mobility management.