The invention discloses a magnetorheological damper piston assembly with a sedimentation active dispersing device. The magnetorheological damper piston assembly comprises a working cylinder, a pistonrod and a piston assembly; the working cylinder is internally provided with magnetorheological fluid; the upper end of the piston rod penetrates into the working cylinder, and the part, penetrating out of the working cylinder, of the lower end of the piston rod is provided with an oil seal; the piston assembly includes a rotor, a stator, a top cover and a bottom cover; the outer circumferential wall of the rotor is provided with spiral ribs; the rotor is arranged on the piston rod in a loose sleeving manner and is located inside the working cylinder; the stator is arranged on the rotor in a sleeving manner and is located inside the working cylinder; a damping gap is formed between the stator and the rotor; the top cover is installed on the piston rod in a sleeving manner and is located inthe working cylinder; and the bottom cover is located in the working cylinder. The spiral ribs on the rotor rotate to make the magnetorheological fluid flow in the working cylinder through the dampinggap to do rotating flow and axial flow, redispersion after sedimentation of the magnetorheological fluid is achieved, and energy recovery when a magnetorheological damper normally runs is facilitated.