Under the promotion of renewable energy, some rural areas have set up disaster-prevention and islanded microgrids composed of decentralized power generation and energy storage system as emergency power supply. However, the unstable characteristic of renewable energy may lead to power outage in the microgrid. This paper aims to allow multiple microgrids to jointly extend the power support time through power sharing, and proposes an interconnected microgrid power dispatching control strategy based on edge computing. The microgrid with a higher percentage of stored electricity could transfer electricity to the microgrid with a lower percentage of stored electricity directly. In addition, the demand-side management is also performed under specifically assigned threshold to extend the power support time for the entire interconnected microgrid system in the islanded mode. The performance of proposal is verified with the 100-kW demo site in the campus of National Central University, Taiwan.