The invention relates to a variable-pitch system for detecting a snow covering rate of fan blades. The variable-pitch system comprises a detecting sensor, a detecting signal emitting and receiving device, a data processing device and a control device, wherein the detecting sensor is used for detecting snow covering thickness of the fan blades, a fan blade temperature, environment wind power and awind direction, and comprises a snow covering thickness sensor and a temperature sensor, which are mounted on the fan blades, an environment air speed sensor which is mounted on a fan pole; the detecting signal emitting and receiving device is used for emitting a detecting signal to the detecting sensor and receiving a real-time data signal acquired by the detecting sensor; the data processing device is used for receiving the real-time data signal, processing the real-time data information to obtain fan blade snow covering rate; and the control device is used for performing pitch varying and yawing operation of the corresponding mode on the fan variable-pitch system and the yawing system according to the fan blade snow covering rate. The variable-pitch system can effectively improve fan operation efficiency, improves windy covered snow treatment ability, effectively avoids harm caused by icing of the fan, and protects the fan better.