The invention discloses a self-adjustment magnetorheological fluid single prop. The self-adjustment magnetorheological fluid single prop comprises a hydraulic positioning system and a magnetorheological fluid support system, wherein the hydraulic positioning system comprises a base (1), a positioning block (2), a hydraulic cylinder body (3), a piston column (12), a guide ring (17), a return spring (18), a sealing ring III (19) and a bottom hydraulic oil inlet (20); and the magnetorheological fluid support system comprises a magnetorheological cylinder body (4), a coil (5), an end cover (6), a pressure sensor (7), a support block (8), a cylinder pin (9), a sealing ring I (10), a separation magnetic ring (11), a piston column (12), an upper magnetorheological fluid injecting port (13), a magnetorheological fluid (14), a sealing ring II (15) and a connecting steel wire (16). The self-adjustment magnetorheological fluid single prop needs no pump station to provide great support, has no need to mount a valve base of a three-purpose valve, is lower in processing requirements on sealing pieces and inner surfaces of mobile columns, and can preferably and automatically adjust the support strength when support loads are suddenly changed.