A device for controlling a high voltage direct current (HVDC) transmission system is provided. The device includes: a communication unit communicating with a control device; a control unit obtaining a databack signal received through the communication unit, checking a data line error and a line connection error based on an obtained databack signal, and outputting a valve control signal based on the databack signal; and an output unit outputting the valve control signal to a valve control device based on control of the control unit.