The utility model discloses an ultra -high voltage direct current transmission line combined material cross arm transmission tower slewing mechanism, its one end is located combined material cross arm (2) end, and the other end is connected with transmission tower (1), its characterized in that: it includes axis of rotation (3), sleeve (4), otic placode (5), otic placode bolt (6), apron (7) and bottom plate (8), axis of rotation (3) for the vertical circular steel column the placed body, axis of rotation (3) the bottom with bottom plate (8) be connected, the top with apron (7), combined material cross arm (2) rotate round axis of rotation (3) through sleeve (4), sleeve (4) for circle annular component, it is increasing to the demand of steel that it has overcome among the prior art construction of special high voltage electric network, has consumed a large amount of mineral products energy to cause ecological environment's tight heavy pollution's shortcoming, have the iron tower of reduction atress, save the tower material, have better economic benefits and social.