The invention discloses a three-phase highly synchronously adjustable transformer, which comprises three pairs of single-phase transformer coil groups, a reduction box, screw rod rotating shafts and electromagnetic clutches, wherein each pair of single-phase transformer coil groups comprises a primary coil and a secondary coil which are wound on an iron core; a fluted disc sleeves the periphery of each secondary coil; an inner ring of each fluted disc is in meshed connection with the periphery of the corresponding secondary coil; a conducting ring is arranged at the upper end of each fluted disc, and is attached to the periphery of the corresponding secondary coil; the reduction box is provided with a motor; an output shaft of the motor is connected with an input shaft of the reduction box; the motor is connected with a controller of the transformer; a rotor gear is arranged at the upper end of each screw rod rotating shaft; each screw rod rotating shaft is in meshed connection with the outer ring of the corresponding fluted disc; and each electromagnetic clutch is selectively connected with the corresponding rotor gear and the output shaft of the reduction box, and is connected with the controller. By the adjustable transformer disclosed by the invention, the technical problem that a three-phase adjustable transformer cannot be transformed into a single-phase adjustable transformer for use is solved.