The present invention discloses a rotor of wind energy conversion system (WECS) with the Venturi-tube effect. All the blades mounted on the blade-mounting seat envelop together to form a revolving-body cage turbine, which can be divided from structure into a head portion at the windward end, a tail portion at the wind exhaust end, and an airstream compression portion between the head portion and the tail portion and constituted by the enveloping blades. The revolution diameter of the airstream compression portion is gradually substantially increased from the head portion to the tail portion. The cage turbine forms a dynamic Venturi tube during the revolving process, with which the blade revolves to constitute its outline tube wall with the air permeability. The airstream passes through a window between the blades, and the incoming wind does work towards the blade during the process of permeating from the external space to the internal space of this outline tube wall, thus realizing the energy transfer.