According to the theory of converter firing control and protection, this paper analyzes the valve control system’s merits and demerits compared with different techniques based on the actual situation of the HVDC and UHVDC transmissions. Siemens valve control system is sequential. It could verdict the protective pulse accurately during the conducting state, but could not do it because of the unperfect control strategy, during the recovery period. ABB valve control system is simple and reliable. But during the firing pulse appeared, it could not distinguish the firing pulse sent again because of the discontinuous current and the protective pulse accurately, and would make the protective trigger faulty act, in the OLT mode or under the small DC load.