The invention relates to the technical field of wind power generation, and discloses a control method and device for inhibiting overspeed of a rotor of a wind generating set, and the method comprises the steps: monitoring the rotating speed of the rotor of the wind generating set in real time, and giving an overspeed alarm and entering an overspeed control mode when the rotating speed of the rotor is greater than a fault rotating speed value; according to the overspeed control mode, the variable-pitch speed of the unit is controlled to be the variable-pitch speed during fault shutdown, the variable-pitch given angle is controlled to be the safe shutdown angle of the unit, and the torque is controlled to be in the constant-power control mode. When the rotating speed of a rotor is larger than a fault rotating speed value, unit shutdown operation is not carried out, overspeed alarm is carried out, an overspeed control mode is entered, in the overspeed control mode, rapid propeller retracting action is carried out by controlling the variable propeller speed, the variable propeller given angle and the torque of the unit, it is guaranteed that the load of the unit is within a safe range, and therefore the fault time is effectively shortened, and the working efficiency is improved. The economic benefits are guaranteed; moreover, the method does not relate to hardware transformation, only relates to software optimization, and is low in transformation cost.