Multi-core transmission system is expected to solve the problem of high-capacity data transmission in the future. However, in the whole communication system, the relay of multi-core signal faces many difficulties, such as the imbalance of channel gain, the beam splitting coupling of multi-core pump light and so on. The uniform coupling between pump light and gain multi-core fiber core determines the efficiency of multi-core fiber gain, the balance of corresponding core gain and the utilization of system energy efficiency, which has become one of the key problems of multi-core system amplification. Based on this, this paper designs a metalens coupling device based on the end face of the optical fiber. By properly optimizing the distribution of the metalens structure, the pump light can focus on the focal plane of the coupled multi-core optical fiber. Compared with the space optical coupling optical fiber system, the waste of pump light is reduced. The theoretical design and numerical simulation results show that the light in the optical fiber cladding can be focused on the end face of the optical fiber, so that the pump light can be shunted and focused on the core, and the total light intensity utilization rate is more than 90%, which provides a solution for the subsequent active optical fiber to realize the core pump.