The invention discloses a power variable stay cable permanent magnet eddy current retarder and belongs to the field of bridge structural vibration control. The power variable stay cable permanent magnet eddy current retarder comprises a rigid shaft, a second linear movement mechanism, a fixed disc, a conductor disc, a driving gear, at least three driven gears of different radiuses, and at least one pair of permanent magnets opposite in magnetic poles; one end of the rigid shaft is connected with the second linear movement mechanism, and the other end of the rigid shaft sequentially penetratesthrough the fixed disc, the conductor disc and the driven gears; the fixed disc is fixed relative to the rigid shaft, the conductor disc is fixed relative to the driven gears, and the driven gears areconnected with the rigid shaft through bearings; the permanent magnets are arranged on the surfaces of the fixed disc. According to the power variable stay cable permanent magnet eddy current retarder, the conductor disc moves inside the magnetic field of the permanent magnets to cut magnetic lines to produce eddy current damping and accordingly to dissipate vibrating energy of a stay cable and inhibit vibration of the stay cable; through engagement between the driven gears different in radius and the driving gear, the energy consumption power can be adjust, high adaptability to external loadcan be achieved, and the power variable stay cable permanent magnet eddy current retarder can be in an optimum load operating sate for a long time.