A drilling system, comprising: a rotatable drill string (110; 310) for connecting with a drill bit for drilling a borehole; at least one fixed stabilizer fixed on the drill string (110; 310; 410) and having an outer surface for contacting a wall of the borehole; and an active stabilizer (150; 350; 450) comprising: a body (351; 451) having an outer surface (352; 452) for contacting a wall of the borehole, and an inner surface (353; 453) facing the drill string (110; 310; 410); and a plurality of actuators (354; 454) connecting the body (351; 451) and the drill string (110; 310; 410), the plurality of actuators (354; 454) capable of driving the drill string (110; 310; 410) to deviate away from a center of the borehole with a displacement, characterised in that: the body (351; 451) of the active stabilizer (150; 350; 450) has at least one guiding portion (359, 360) projecting from the inner surface (353; 453) towards the drill string (110; 310; 410), each guiding portion (359, 360) defining at least one groove (361, 362), wherein the drill string (110; 310; 410) comprises at least one sliding portion (363, 364), each capable of sliding within one of the at least one groove (361, 362) defined in the body (351; 451) of the active stabilizer (150; 350; 450), to constrain relative movement between the drill string (110; 310; 410) and the active stabilizer (150; 350; 450) along an axial direction of the drill string (110; 310; 410) and guide relative movement between the drill string (110; 310; 410) and the active stabilizer (150; 350; 450) along a radial direction substantially perpendicular to the axial direction of the drill string (110; 310; 410). a rotatable drill string (110; 310) for connecting with a drill bit for drilling a borehole; at least one fixed stabilizer fixed on the drill string (110; 310; 410) and having an outer surface for contacting a wall of the borehole; and an active stabilizer (150; 350; 450) comprising: a body (351; 451) having an outer surface (352; 452) for contacting a wall of the borehole, and an inner surface (353; 453) facing the drill string (110; 310; 410); and a plurality of actuators (354; 454) connecting the body (351; 451) and the drill string (110; 310; 410), the plurality of actuators (354; 454) capable of driving the drill string (110; 310; 410) to deviate away from a center of the borehole with a displacement, a body (351; 451) having an outer surface (352; 452) for contacting a wall of the borehole, and an inner surface (353; 453) facing the drill string (110; 310; 410); and a plurality of actuators (354; 454) connecting the body (351; 451) and the drill string (110; 310; 410), the plurality of actuators (354; 454) capable of driving the drill string (110; 310; 410) to deviate away from a center of the borehole with a displacement, characterised in that: the body (351; 451) of the active stabilizer (150; 350; 450) has at least one guiding portion (359, 360) projecting from the inner surface (353; 453) towards the drill string (110; 310; 410), each guiding portion (359, 360) defining at least one groove (361, 362), wherein the drill string (110; 310; 410) comprises at least one sliding portion (363, 364), each capable of sliding within one of the at least one groove (361, 362) defined in the body (351; 451) of the active stabilizer (150; 350; 450), to constrain relative movement between the drill string (110; 310; 410) and the active stabilizer (150; 350; 450) along an axial direction of the drill string (110; 310; 410) and guide relative movement between the drill string (110; 310; 410) and the active stabilizer (150; 350; 450) along a radial direction substantially perpendicular to the axial direction of the drill string (110; 310; 410). the body (351; 451) of the active stabilizer (150; 350; 450) has at least one guiding portion (359, 360) projecting from the inner surface (353; 453) towards the drill string (110; 310; 410), each guiding portion (359, 360) defining at least one groove (361, 362), wherein the drill string (110; 310; 410) comprises at least one sliding portion (363, 364), each capable of sliding within one of the at least one groove (361, 362) defined in the body (351; 451) of the active stabilizer (150; 350; 450), to constrain relative movement between the drill string (110; 310; 410) and the active stabilizer (150; 350; 450) along an axial direction of the drill string (110; 310; 410) and guide relative movement between the drill string (110; 310; 410) and the active stabilizer (150; 350; 450) along a radial direction substantially perpendicular to the axial direction of the drill string (110; 310; 410).