The invention discloses a direct current power supply automatic control device. The direct current power supply automatic control device includes a direct current contactor KM and a direct current voltage detection controller; two ends of a normally-open main contact of the direct current contactor KM are connected with a first direct current power source bus HM1 and a second direct current power source bus HM2 respectively; a coil of the direct current contactor KM is connected with a control loop of the direct current voltage detection controller; and the direct current voltage detection controller is provided with a first voltage detecting end J1 used for detecting the voltage of a storage battery pack which is connected with the first direct current power source bus HM1 and a second voltage detecting end J2 used for detecting the voltage of a storage battery pack which is connected with the second direct current power source bus HM2. With the direct current power supply automatic control device adopted, a bottleneck that mutual standby application of an operating power source system and a communication power source system of an existing substation and power plant can be only realized manually can be broken. The direct current power supply automatic control device is advantageous in simple structure, high reliability and conduciveness in promotion and usage.