The interconnected multi-microgrid (IMG) has brought new benefits technically and economically. However, the interconnection may lead to impulse voltage in each microgrid. Furthermore, due to different capacities of MGs, there is the frequency fluctuation in interconnected line after interconnection of microgrids. In this paper, a coordinated control strategy was proposed to restrain the transient fluctuation of voltage when interconnecting. Then, referring to different capacities of each microgrid, the proposed control strategy also adopts automatic generation control (AGC) to keep the balance of power in interconnected line, which further to suppress system frequency fluctuation. In the model of three microgrids, simulation was conducted by Digsilent/PowerFactory under hierarchical control system. The results show that the proposed control strategy in this paper restrains voltage fluctuation when interconnecting as well as suppresses frequency fluctuation after interconnecting effectively.