The invention discloses a method and device for detecting freezing of wind generating set blades. The method comprises the steps that A, environment temperature and humidity, the wind speed, the wind direction, the position of an engine room, the pitch angle of the blades and generator power are acquired; B, data generated in a non-freezing state and in the process that the yaw error of a draught fan is too large is removed; C, the power and pitch angle calculated values under the actually-measured wind speed is obtained according to a wind speed power matrix and a wind speed pitch angle matrix; D, the difference value of the generator power and pitch angle actually-measured values and the calculated value are compared with a deviation set value, the set value is corrected, and a deviation optimized value is obtained; E, the deviation between the power and pitch angle monitored in real time and the power and pitch angle calculated according to the wind speed power matrix and the wind speed pitch angle matrix is compared, and when the deviation meets the deviation optimized value, it is judged that the blades are in a frozen state. According to the method and device, the freezing state of the wind generating set blades can be detected accurately and reliably, effective early warning and maintenance can be achieved, and therefore the generating capacity and stability of a set are improved, and the service life of the set is prolonged.