The invention discloses an intelligent identification method of a transient inability mode of a power grid. The intelligent identification method comprises the steps: step A, defining a dominant instability cluster formed by a generator set; step B, calculating dominant instability generator identifying indicators of each generator in the dominant instability cluster under special faults and identifying the seriously disturbed generator unit in the dominant instability cluster according to the dominant instability generator distinguishing indicators; and step C, carrying out topological clustering for the generators in the seriously disturbed generator unit and realizing the identification of the dominant instability cluster. According to the intelligent identification method of the transient inability mode of the power grid, the instability mode and the dominant instability cluster of the power grid can be directly identified according to the topology and the operational mode of the power grid so as to offer supports to transient stability evaluation and control decisions; and the efficiency and property of the transient stability evaluation and control decisions can be improved effectively.