There are 9 operating modes for expanded inter-bridge connection and as many as several dozen logics for backup power automatic throw-in. At present only 4 operating modes have been put into operation and each mode adopts only one control logic， so that its application is limited. A novel adaptive backup power automatic throw-in device for expanded inter-bridge has been developed and introduced. All of logic relationships have been summarized and extracted to form one adaptive fundamental control logic， which can be implemented simply and adapted to different operating modes. The experiments and test operation results in a 110 kV substation prove that the device can satisfy different control logics of different operating modes with expanded inner-bridge.