The present invention provides a monitoring and alarming system for a DC power supply in a transformer substation. A DC power supply side monitoring module in the system is used for monitoring a charger, a bus and a storage battery in the transformer substation in real time and sending the monitoring data to a central processing module. The central processing module is used for receiving the monitoring data of the DC power supply side monitoring module, generating an alarm command when the monitoring data is abnormal, sending the alarm command to the alarm fire fighting module, and sending the received monitoring data and a telecommand signal generated accoridng to abnormal monitoring data to a remote monitoring center. The alarm fire fighting module receives the alarm command and extinguishes a fire on target abnormal equipment according to the alarm command. According to the system, the DC power supply is monitored in real time and the fire is extinguished timely, the safety and stability of DC power supply operation are improved, the human cost is reduced at the same time, the danger is controlled in a controllable range, and the stability of the transformer substation is improved greatly.