The invention discloses a method for rapidly calculating the wind curtailment rate of a power grid wind power plant and the generating capacity of a unit. The method comprises the following steps: (1) predicting a load curve of a power system, determining a scheduling period of the power system, and forming an interval load curve according to the load curve predicted by the power system and the scheduling period; (2) determining a start-up mode according to the interval load curve in the previous step, and predicting the predicted load curve according to the determined start-up mode; (3) predicting wind power according to wind speed information of the wind power plant, building a wind power model, and rapidly calculating the on-grid energy and the wind curtailment rate and correcting the load curve according to the predicted wind power and the load curve corrected in the previous step; and (4) calculating the generating capacity of a start-up unit by an equivalent energy function method according to the load curve corrected in the previous step. According to the method, complicated optimization problems can be decomposed into a few of relatively simple constraint problems when the actual condition of the power system is considered; and the optimization problems are connected through data flow, so that the wind curtailment rate of a regional power grid is rapidly calculated.