Owing to frequent occurrence of large-scale wind turbines cascading disconnection from the power grid，it is imperative to study the causes as well as corresponding preventive measures for these accidents.A real wind power delivery case with detailed power network topology and parameters is modeled，based on which the transient process of large-scale wind turbines cascading disconnection is replayed.The dynamic reactive power response capabilities of wind turbines and reactive power compensation devices during the transient process are analyzed.A reactive power and voltage emergency control strategy considering the above dynamic reactive power response capabilities is proposed.In the proposed emergency control strategy，the grid-side converters of wind turbines are utilized to dynamically provide reactive power to the grid to mitigate voltage drop in real time.In addition，reactive power compensation devices are actively disconnected from the grid before fault removal to restrain the transient overvoltage，and then reconnected to the grid according to the voltage level in the recovering period to provide reactive power support.Simulation results validate the feasibility and effectiveness of the proposed control strategy.