The invention relates to an automatic backup silicon chain switching device for a direct-current system. A control bus is monitored in real time by two voltage relays connected to the control bus; and when the two voltage relays simultaneously judges that the control bus generates voltage loss, normally open contacts of a direct-current contactor are controlled to be closed through the electrified actuation of coils of the direct-current contactor, so that a backup silicon chain which is in the 'hot backup' state is switched instantly to replace the original silicon chain for running, and simultaneously, an alarm signal is sent to an integrated automation system. The automatic backup silicon chain switching device has the characteristics of high action speed, small volume, low cost, settable voltage, safety, reliability and the like.