The invention relates to a high-voltage direct-current power transmission TTM board card fault positioning system and fault positioning method thereof. The system includes a wave recording monitoring system, a VBE and a valve module which are connected in sequence, a thyristor triggering monitoring unit TTM board card in the valve module collects and processes a node signal that a converter valve needs to monitor, soon afterwards a processing judgment signal is transmitted to a signal collection communication board, and the signal is stored in a storage chip of the signal collection communication board; when a triggering monitoring case of the VBE detects that the TTM board card of a certain stage or multistage thyristor sends an overvoltage protection return pulse, energy taking return pulse disappears or the signal collection communication board detects a key signal abnormality of itself, wave recording is automatically started or wave recording is started in a manual mode; and a fault recording device performs fault positioning. The high-voltage direct-current power transmission TTM board card fault positioning system provided by the invention solves the problem that in a high-voltage direct-current power transmission converter valve body, under the working condition of strong electromagnetic field interference, tracking of a TTM board card key signal node cannot be realized in a fault section.