The invention discloses a weak stability mode memory-based emergency control method for the system transient stability, and belongs to the technical field of power systems and automation thereof. The problem of system online emergency control on the transient safety and stability of a weak stability mode is solved by a massive parallel cluster computing technology; a transient power angle stability emergency control strategy under the influence of multimode interaction is calculated; if other potential instability modes are excited in a safety check process of a dominant instability mode control measure scheduling sequence, transient safety and stability quantitative evaluation of the dominant instability mode control measure scheduling sequence is terminated and a potential instability mode control measure scheduling sequence and the back-space dominant instability mode control measure scheduling sequence are subjected to enumeration combination to form a new scheduling sequence; and a parallel cluster system is resubmitted for transient safety and stability quantitative evaluation, so that coordination of control measures among multiple instability modes is achieved.