The invention relates to a device for the improvement of aerodynamic performance of a flexible blade of a large wind machine. The device comprises a blade aeroelastic response monitoring system, a data integration and processing system, a blade steering system, an added mass adjustment system and a vortex generation system, wherein the blade aeroelastic response monitoring system consists of an intelligent monitoring control unit, a data acquisition unit and a sensor; the data integration and processing system consists of a response converter, a vibration mode recognizer and an instruction generation module; the blade steering system consists of a control receiver, a posture adjustment module, a mechanical telescopic arm and fixing bolts; the added mass adjustment system consists of a control receiver, a water collecting tank, a water delivery pipe and a flow control valve; the vortex generator consists of a vortex generator part, tandem bolts and an actuator. The device is applicableto the field of wind machine safety design, an aeroelastic phenomenon of the flexible blade of the ultra large wind machine in a flow field can be inhibited effectively, and safe operation of the windmachine under the action of various natural flow fields is ensured.