The invention provides a traction substation busbar potential transformer on-line monitoring automatic apparatus which is characterized by including an MCU, a real-time clock, an LED driver, an LCM interface, two interfaces, an analog input and conditioning unit, a communication interface, a power supply, a control outlet, a dead contact output unit, and a terminal. The MCU, the real-time clock, the LED driver, the LCM interface, and one interface form a main board, and the analog input and conditioning unit, the communication interface, the power supply, the control outlet, the dead contact output unit, and the terminal form an input and output board. The traction substation busbar potential transformer on-line monitoring automatic apparatus is advantageous in that the design is reasonable and the operation is reliable, the automatic, intelligent, time-interval-free switching and monitoring of YH can be realized, under the condition that the running YH has faults, data can be imported to another well-run YH timely and intelligently before the misoperation of a protection device, the voltage of the standby YH can be supervised and predicted and can be monitored in real time, and when the state or accessories have the trend to deteriorate, the early warning is timely sent to remind the attendant checking and processing.