Abstract: The stability of links in mobile cognitive radio network is significantly affected by primary user activities and node mobility. These two factors make the topology control in mobile cognitive radio network more challenging than traditional wireless networks. The instability of network topology is caused by the difference between the secondary users and the priority of the primary user in the network. For above reasons，this paper proposes an estimation model of link available time based on primary user prediction. Compared with the other existing estimation methods，the primary user activities are considered as the basis that the secondary users are interfered by the primary user，rather than whether the secondary users enter the interference radius of the primary user. Based on the above model，the available duration of the link can be estimated，and it can be taken as the objective of the topology control algorithm based on the enhanced maximum spanning tree algorithm，which maximizes network topology retention time，avoids the network topology frequent reconfiguration and reduces the network topology retention cost. Simulation results show that the topology control algorithm based on the primary user activity is more accurate for estimating the available duration of the link，and also ensures the maximum duration of the network topology.