The invention discloses a bending blank manufacturing method for stainless steel flash welding thin-wall ring profiles. The method comprises the steps that a stainless steel profile fed according to specifications is divided into five segments of mn, no, op, pq and qw, heated to a temperature of 720 DEG C+/-20 DEG C and fed in a bending machine for positioning. The op segment is bent, rotation linear speeds of an upper roller and two lower rollers are 2400 mm/min, the upward moving speeds of the two lower rollers are 10.0 mm/min, the bending is repeated for 3 times, and the op arc segment at this moment achieves a preset curvature radius; and the no segment and the pq segment are bent, the rotation linear speeds of the upper roller and the two lower rollers are 1200 mm/min, the downward moving speeds of the two lower rollers are 12.7 mm/min, the bending is repeated for 3 times, and the no and pq arc segments at this moment achieve preset curvature radii. The profile is bent and deformed into a D-shaped ring blank, two straight sides and an arc portion of the ring blank are connected through a transition arc segment, and phenomena of bent angles at connection positions of the two straight sides and the arc portion and indentations on the surface of the ring blank are eliminated.