The invention discloses an unfolding mechanism of a flexible solar wing for a space station. The quality limitation of rigid solar cell arrays becomes a prominent problem. The unfolding mechanism comprises a bottom storage box, a storage barrel body, a storage barrel lid, an extension arm unfolding mechanism, a top storage box, a triangular prism extension arm, an airfoil and an airfoil tensioning mechanism, wherein a bottom tripod of the triangular prism extension arm is fixedly connected with a boss in the storage barrel body, and the top tripod is fixedly connected with the barrel lid; the top storage box is fixedly connected with the storage barrel lid, and the bottom storage box is fixedly connected with the storage barrel body; the extension arm unfolding mechanism is fixed at the bottom of the storage barrel body and controls an extension arm to be unfolded at the constant speed; the airfoil tensioning mechanism is fixed in the top storage box, guarantees tension to a solar wing during unfolding, tensions the solar wing after unfolding and keeps certain rigidity. The solar wing is small in mass, the airfoil and the extension arm occupy small size after being folded, and the extension arm can be reliably locked after being unfolded.