The invention discloses a stabilizing device, a floating foundation and an offshore wind power generator. The stabilizing device comprises a U-shaped water chamber, wherein the U-shaped water chamber comprises a first hollow upright column, a second hollow upright column and a bottom buoyancy tank connected between the bottoms of the two upright columns, the first upright column and the second upright columns are communicated with the bottom buoyancy tank, and the top of the first upright column and the top of the second upright column are communicated through an air communication pipeline. The floating foundation is at least provided with a first upright column, a second upright column and a third upright column, and comprises at least one stabilizing device. The offshore wind power generator comprises the floating foundation, a mooring rope, a tower, vanes and a wind power generator set, wherein the mooring rope is connected with the outer edge of the floating foundation and is anchored to the seabed, the bottom end of the tower is arranged on the floating foundation, and the vanes and the wind power generator set are arranged on the top of the tower. By means of the stabilizing device, stabilizing of a floating fan can be simply and effectively achieved through a double-resonance principle.