The invention discloses a downwind aerogenerator gyrodamping and locking mechanism which mainly comprises an anemoscope, a gear case, a motor, a small belt wheel, a big belt wheel, a synchronous belt and a pedestal flange, wherein the motor is connected with the small belt wheel by the gear case, the small belt wheel is connected with the big belt wheel by the synchronous belt, the big belt wheelis connected and fixed with the pedestal by bolts, a tension wheel is arranged on the supporting frame of the gear case, and the supporting frame is provided with a spring matched with the tension wheel. Rotational resistance is relatively large under the condition of no power supply, and speed change between the transmission of the gear case and the synchronous belt increases torque moment so asto achieve good damping effect. The invention has simple operation, and solves the problems of frequent swinging of a generator and unstable power output caused by the influence of wind change, towershadow effect and other factors in the power generation process of the downwind aerogenerator. The invention increases the work efficiency of the aerogenerator, reduces the wear degree of parts, and is more safe and convenient during maintenance.