The embodiment of the invention provides a magnetorheological damping control method and device for a floating slab track. The magnetorheological damping control method for the floating slab track includes the steps that the best values of the magnetorheological damping force, the displacement threshold value and the response retardation time of a magnetorheological damper are obtained according to a vehicle-magnetorheological damping semi-active vibration isolation floating slab track vertical coupling system dynamics model; and the magnetorheological damping force, the displacement threshold value and the response retardation time of the magnetorheological damper are controlled to be adjusted to the best values through a terrace semi-active switch of the magnetorheological damper. According to the magnetorheological damping control method and device for the floating slab track, the magnetorheological damper is introduced into the traditional floating slab track, the magnetorheological damper is controlled by adjusting the values of the parameters such as the magnetorheological damping force, the displacement threshold value and the response retardation time of the magnetorheological damper, the vibration amplification phenomenon near the inherent frequency of the floating slab track is effectively inhibited, and meanwhile the maximum vertical vibration displacement of the floating slab track is obviously reduced, so that safety of a wheel track is improved.