The invention relates to a chuck of a bend mechanism (7) for a thin-walled tube bending blank. The chuck comprises a material fixing plate (1) connected to the bending mechanism (7) through a connecting pin (5); the material fixing plate (1) is provided with a clamping plate (2); a hook (3) and a hinge pressing plate (4) are further arranged on the material fixing plate (1) above the clamping plate (2); the hook (3) and the hinge pressing plate (4) are connected through a spiral spring; and the hinge plate (4) is provided with a waist groove. The chuck is simple, light and handy in structure,convenient to process, low in cost and wide in application range; and the problems about clamping anti-deformation and positioning of a thin-walled tubular product are solved, meanwhile, the utilization rate of the thin-walled tubular product is maximized to the greatest extent, and the production cost is reduced.