A drilling system includes a drill string for connecting with a drill bit for drilling a borehole, a fixed stabilizer fixed on the drill string, and an active stabilizer including a body and actuators connecting the body and the drill string. The actuators are capable of driving the drill string away from a center of the borehole with a displacement. The body has an outer surface for contacting a wall of the borehole, an inner surface facing the drill string, and at least one guiding portion projecting from the inner surface and each defining at least one groove. The drill string includes at least one sliding portion slidable within the at least one groove respectively to constrain movement between the drill string and the active stabilizer along an axial direction of the drill string and guide movement between the drill string and the active stabilizer perpendicular to the axial direction.