The invention provides an optimizing method and an optimizing device of accessible wind power output during net rack reconstruction. The method includes performing net rack reconstruction after a wind power generator is accessed to an electrical power system to generate a reasonable pre-constructed net rack; according to output fluctuation of large wind power plants in the pre-constructed net rack and adjustment extremums of grid-connected output-adjustable generator units, constructing an optimization model of accessible wind power quantity of the pre-constructed net rack; transforming the optimization model into a general undetermined planning model, namely a two-stage robust optimization model, and solving the two-stage robust optimization model of the accessible wind power quantity of the pre-constructed net rack to acquire an optimized pre-constructed net rack accessible wind power output range. By the method, the wind power generator can be accessed to the electrical power system, the accessible wind power output which can take part in the net rack reconstruction process after blackout can be optimized, and reliability of the recovery process can be improved.