The invention provides a multi-satellite emergency task planning method and device considering instruction injection. According to the method, a plurality of scheduling decision moments are determinedaccording to an observation and control station and a visible time window of each satellite, whether an emergency task is added is judged at each scheduling decision moment, therefore, the added emergency tasks can be timely discovered, and the processing efficiency of the emergency tasks is improved. Available visible time windows of the tasks are screened by use of injection completion time, and therefore it is guaranteed that observation of the relevant tasks is not performed unless injection is completed. When the available visible time windows are selected for the emergency tasks, a completion deadline of the emergency tasks is considered, and therefore it is ensured that the emergency tasks are completed before the predetermined completion deadline. A precise algorithm is utilized to perform task planning on a weighted sum of the emergency tasks and conventional tasks, therefore, a target available time window can be quickly arranged for each emergency task, planning efficiencyand benefit of the emergency tasks can be improved, and the overall task completion rate can be guaranteed.