The utility model discloses an icing device is prevented to outer air -cooled air cooler motor of HVDC converter valve, prevent icing cover and circular heating unable adjustment base including the umbrella -type, circular heating unable adjustment base is hollow structure, and circular heating unable adjustment base internal surface sets up the zone of heating, circular heating unable adjustment base upper surface sets up the annular first recess of circle, and circular heating unable adjustment base lower surface sets up the annular second recess of circle, and circular heating unable adjustment base bottom sets up insulated layer, sets up the power in the insulated layer, insulated layer bottom sets up the switch, and first recess internal surface sets up the frictional layer, second recess bottom sets up insulating skid resistant course, and it is protruding that the umbrella -type prevents that the icing cover is provided with the ring shape of matcing with first groove phase, circular heating unable adjustment base and motor top fixed connection. The utility model discloses simple structure, portable, can disassemble, can effectively prevent the motor icing.