The invention relates to a hand, in particular to a flexible self-adaption under-actuated robot hand. The flexible self-adaption under-actuated robot hand comprises fingers and a wrist; the wrist includes a skeleton, a direct-current motor, a potentiometer and a winch; the direct-current motor is fixedly connected to a motor mounting surface of the skeleton; the potentiometer is fixedly connected to a potentiometer mounting surface of the skeleton by penetrating through an output shaft of the motor; the winch is fixedly connected to the tail end of the output shaft of the motor; multiple fingers are provided; and the fingers are embedded in clamping grooves of the skeleton or multiple clamping grooves through convex blocks of rotating bodies. The flexible self-adaption under-actuated robot hand is assembled at the tail end of an industrial robot for assisting mechanical assembly or mechanical manufacturing process and finishing automatic workpiece loading/unloading; and the fingers can flexibly adapt to geometric shapes of products, and realize automatic adjustment according to the geometric shapes of workpieces to realize stable grabbing.