Abstract: The decentralization of the multi-microgrid system is an important development trend of microgrid. In this paper, we focus on the distributed control strategy of the multi-microgrid system. This paper applies Gossip Algorithm to a composite islanding system composed of several microgrids, presents an electricity trading model of retail market, and aims to minimize the global objective function of the multi-microgrid system. The electricity pricing is achieved in the multi-microgrid based on pairwise equalizing Gossip algorithm. To ensure security and privacy, an improved Gossip algorithm is designed with privacy protection to avoid cost function sharing at the expense of increasing the iteration time. Finally, the effectiveness of the proposed method for the distributed multi-microgrid system in islanding mode is verified by the simulation result of the example.