The invention provides a flue gas discharge apparatus of an all-oxygen kiln, wherein the flue gas discharge apparatus comprises the front gable wall (1) of a kiln, and a flue channel (3) is arranged between the front gable wall (1) and a chimney (2). According to the present invention, the flue gas discharge apparatus has advantages of simple structure and convenient use, can reduce the consumption of refractory bricks in the existing all-oxygen kiln, and has good effects in the temperature system and the kiln pressure control of kilns.