The invention discloses a long-distance automatic stand-by power switching device. The long-distance automatic stand-by power switching device comprises analog input and a switching input and output device, wherein the analog input comprises accessed current and voltage, and the switching input and output device comprises an accessed switching position, a tripping and switching-on command and a voltage/non-voltage contact. According to the device, communication between transformer substations is realized by virtue of fiber channels, i.e., a photoelectric conversion device is installed on each transformer substation, transmission of voltage, the switching position and the tripping/switching-on command is carried out by virtue of optical cable connection, criteria of the switching position of the switching input and output device and voltage transmission or non-voltage transmission of buses are received by the photoelectric conversion device and then sent to the long-distance automatic stand-by power switching device accessed to the transformer substations, and simultaneously, the tripping and switching-on command is transmitted. The long-distance automatic stand-by power switching device has the advantages of safety and reliability, incoming line automatic stand-by power switching, segmented automatic stand-by power switching and long-distance automatic stand-by power switching functions can be realized, and the power supply reliability is increased.