The embodiment of the invention provides a method and device for monitoring icing of blades of a wind generating set. The method comprises the following steps of judging whether the current power generation working condition of the wind generating set is a rated power power-generation working condition or a limited power power-generation working condition or not; calculating an actual pneumatic coefficient of the current blades if the current power-generation working condition of the wind generating set is the rated power power-generation working condition or the limited power power-generationworking condition; acquiring a standard pneumatic coefficient corresponding to a propeller pitch angle of the current blades according to a mapping relation between the propeller pitch angle and thestandard pneumatic coefficient of the blades; and determining the icing of the blades if a difference value between the standard pneumatic coefficient of the current blades and the actual pneumatic coefficient of the current blades is more than a first preset alarm threshold value. Because the icing of the blades is judged by utilizing original data of the wind generating set instead of adoption of an icing sensor, the cost of the wind generating set is reduced, and the complexity of processing signals through the wind generating set is reduced.