The invention belongs to control technology of an electric power transmission and distribution network, and relates to a method for verifying correctness of decoupling an operation mode of expanded inner bridging line standby power automatic switching. The method is applied to a standby power automatic switching decoupling device of a power substation of which the power transmission and distribution network is at a voltage level of 220 kV or lower than 220 kV and a primary main connecting line is a double-power supply expanded inner bridging line. In a specific method for verifying correctness of decoupling the operation mode of a standby power supply automatic switching device with a double-power supply expanded inner bridging line, a logic algebraic expression of decoupling the operation mode of expanded inner bridging line standby power automatic switching is shown in the description in detail. The advantages of the method for verifying correctness of decoupling the operation mode of expanded inner bridging line standby power automatic switching are reflected in that: 1: using logic algebra for checking calculation of ''decoupling'' of the operation mode of the expanded inner bridging line standby power automatic switching device is simple and clear; and 2. the method of using logic algebra for checking calculation of ''decoupling'' the operation mode of the expanded inner bridging line standby power automatic switching device is convenient to implement and easy to understand.