The utility model discloses an outer air -cooled air cooler low temperature drainage device of HVDC converter valve, including pressure nitrogen gas jar, valve, outer air -cooled air cooler and liquid storage pot, the control unit, income valve temperature transmitter, play valve temperature transmitter and pressure transmitter, go into valve temperature transmitter and set up in outer air -cooled air cooler and the pneumatic pipeline of adjusting between the butterfly valve, in play valve temperature transmitter set up the pipeline between outer air -cooled air cooler and magnetic ball valve, pressure transmitter set up in the pipeline between electromagnetism relief pressure valve and needle type valve. The utility model discloses temperature and pressure in can the real time monitoring pipeline, according to temperature in the pipeline and pressure data, aperture that the system can automatic, real -time each valve of regulation have improved the automatic level of system to when temperature and pressure value exceed normal working range, can provide alarm signal for the operation personnel, ensured the system security steady operation.