A bullhead-shaped grooved diversion jet and empennage swing vibration suppression device and method. The device consists of an impeller diversion module and a drainage rotary cover module. The impeller diversion module consists of a center impeller, sleeve bearings, small impellers, and small impeller rotating shafts. The drainage rotary cover module consists of a drainage front cover, a perforated jet rear cover, and empennages. The device is mounted on an outer wall of a riser in a sleeving manner. Under a combined action of drainage and space allocation of horizontal rectangular grooves, flow rate distribution of the center impeller, flow direction adjustment of the small impellers, diversion of lateral diversion holes, jet flows of side rear reducing holes, flowing space division and wake vortex turbulence of rotary swinging empennages, around-flow boundary layers at two sides and a tail of the riser are deeply damaged, which suppresses the formation of large vortexes.