The invention discloses a flame tube with a novel cooling structure. The flame tube comprises a combustion chamber casing, wherein a flame tube body and a large elbow are arranged in the combustion chamber casing, an inlet diffuser is arranged on one side of the combustion chamber casing, a lap joint section is arranged in the combustion chamber casing and between the flame tube body and the large elbow, an outer ring main combustion mixing hole is formed in an outer ring of the flame tube body, a head swirler mounting hole is formed in a head ring of the flame tube body, an inner ring main combustion mixing hole is formed in an inner ring of the flame tube body, the flame tube body comprises the outer ring, the head ring, the inner ring and a small elbow, the outer ring, the head ring, the inner ring and the small bent pipe of the flame tube body are of an integrated structure, and zigzag small-aperture circular cooling channels are formed in the wall faces of the outer ring, the head ring, the inner ring and the small elbow of the flame tube body and the wall face of the large elbow respectively, so that the number of holes formed in the wall faces is greatly reduced, cracks of the holes are reduced, and the service life of the flame tube body is prolonged.