Massive Multiple-Input Multiple-Output （MIMO） is one of the key technologies in 5G. Pilot contamination, which is caused by limited number of pilots, has become an important bottleneck for the development of massive MIMO. In this respect, a reasonable pilot allocation should be designed for the valuable pilot resources to reduce the effect of pilot pollution. However, existing pilot allocation schemes mostly consider static pilot allocation, which are not well adapted to the mobile communication environment where user positions are constantly changing. In this paper, a dynamic migration pilot allocation algorithm is proposed for the problem of how pilots are dynamically allocated stepping with the movement of users in massive MIMO. According to pilot allocation algorithm, a user is selected to exchange pilots with the user who has migrated between two time slots and does not change the original allocation pilot for other users. The complexity analysis and simulation results show that the proposed algorithm can significantly reduce the computational complexity and have similar spectral efficiency comparing with the traditional pilot allocation method. Therefore, the proposed algorithm has a high practical significance.