Air lock for pre-oxidizing furnace

The utility model provides an air lock for a pre-oxidizing furnace, and aims to solve the problems of the conventional pre-oxidizing furnace that the pre-oxidizing furnace has an opened port, so that plenty of hot wind can overflow from the port when used for heating and pre-oxidizing filament in a hearth, and leading to the heat loss and pollution due to the waste gas. The air lock comprises a lock housing, wherein a carbon filament channel is arranged at the centre of the lock housing, and separates the lock housing into an upper lock housing and a lower lock housing; an upper vertical air port is arranged at the lower end of the upper lock housing, and a lower vertical port directly facing the upper vertical air port is arranged at the upper end of the lower lock housing; an upper angle air port is arranged at one side of the lower end of the upper lock housing, close to the hearth, and inclined from an internal chamber of the upper lock housing to the hearth; and a lower angle air port symmetric to the up