Emergency missions of multi-satellite observation have sudden and uncertain natures, unlike mission planning for regular tasks, emergency mission planning needs to respond quickly to mission requirements. The multisatellite emergency mission planning considers the key factors that restrict the emergency task planning including instruction release and data download, so a task scheduling mechanism based on fixed cycle scheduling and localadjustment scheduling is designed. On this basis, under the condition of downloading the emergency mission as soon as possible, a two stage algorithm is proposed to solve the dynamic problem of emergency mission. Finally, The experimental results indicate the effectiveness of the proposed algorithm to solve the emergency mission planning problem.