The invention relates to a unidirectional pulley. An inner ring body is sleeved outside a mandrel connecting sleeve, a pulley is sleeved outside the inner ring body, the left end and the right end of the mandrel connecting sleeve are sleeved with bearings, the inner surfaces of inner rings of the bearings are in contact with the outer surface of the mandrel connecting sleeve, the outer surfaces of outer rings of the bearings are in contact with the inner-hole wall surface of the pulley, the inner ring body sleeve is sleeved outside the mandrel connecting sleeve arranged between the opposite end surfaces of the two bearings, the outer surface of the mandrel connecting sleeve arranged between the opposite end surfaces of the two bearings is provided with a curved surface die cavity, a roller pin is arranged in the curved surface die cavity, the cross section of the curved surface die cavity is in a wedge shape, the small end of the curved surface die cavity is consistent with a rotatingdirection of an electric generator in a working process, the large end of the curved surface die cavity is provided with a restoring spring, the restoring spring is supported to the roller pin and pushes the roller pin to the small end of the curved surface die cavity, and a sealing device is sleeved on the mandrel connecting sleeve. The unidirectional pulley eliminates the phenomenon that the pulley skids when running at high speed and solves the conflict between spring thrust and frictional resistance.