The invention discloses a fan variable-pitch optimizing method based on rotation-speed-limited smooth power control. Aiming at solving the problem of frequent pitch changing of a fan under the air condition of high air speed, the method sufficiently uses the large rotational inertia air wheel kinetic energy buffering/release function of any pitch angle and achieves the rotation speed interval control of the fan under any pitch angle on the basis of reducing the output power fluctuation of the fan based on rotation-speed-limited smooth power control. Through cooperative use of the variable-speed adjustment and variable-pitch adjustment, the smooth variable-speed adjustment causes power fluctuation due to small-amplitude and high-frequency air speed fluctuation, and the variable-pitch adjustment responds to the large-amplitude and low-frequency air speed changes. The power grid frequency fluctuation caused by power fluctuation is within the power grid allowable range. The amplitude and frequency of the variable-pitch action are reduced effectively, the fatigue degree and blade loads of a variable-pitch servo mechanism are reduced, and the service life of the fan is prolonged.