The invention provides a mobility management method based on a clustered superdense small network in a 5G system. The mobility management method comprises the following steps: dividing a superdense cell into a plurality of microcell clusters, wherein each microcell cluster has a common pilot frequency; predicting the channel condition of the cell by using a birth-death model, and according to the quality of a received cell signal, comprehensively considering the business condition and the mobility state of a user terminal and selecting a proper base station as a switching target, wherein the blocking rate of new equipment calling and switching can be obtained, a correct switching strategy is established, the switching success rate is improved, and the call drop rate of the user terminal and the blocking rate of calling are reduced; when equipment is in an idle state and the user terminal is in a low-speed state, switching to a pilot frequency base station of a microcell; when the user terminal is in a medium-speed or high-speed state, switching to a macro base station; when the equipment is in a connection state, namely when a business service exists, if the user terminal is in the low-speed state, switching to a small base station of the microcell; when the user terminal is in the medium-speed or high-speed state, switching to the macro base station.