The invention discloses a spinning reserve capacity optimization method based on a backup object performance ratio, and belongs to the technical field of electric power system automation. According to the invention, on the basis of a total cost of a spinning backup object (hereinafter called backup object) under a target power space curve scenario set (hereinafter called target scenario set) and an efficient backup electric quantity which can be provided, a price performance ratio of the of the spinning backup object is calculated. According to the invention, the cost and the performance of the backup object can be comprehensively considered. A better optimization effect can be obtained compared with the optimization effect realized through optimization configuration carried out according to the capacity price of the backup object or according to the sum of the capacity price and the electric quantity price multiplied by the probability of occurrence. Meanwhile, the method of the invention can directly realize unified optimization of sending and needing and avoid a large amount of calculation in a decoupling-iteration process between the sending side and the needing side.