The invention belongs to the technical field of transformers and discloses a phase-shifting winding type voltage-regulating rectifier transformer and a voltage regulating method thereof. A transformer cabinet internally comprises a phase-A core limb, a phase-B core limb and a phase-C core limb which are wound by two groups of phase-A windings, phase-B windings and phase-C windings respectively. A long-side dotted terminal of a high-voltage-side base winding in each group of three-phase windings is serially connected with a short-side dotted terminal of an adjacent-phase phase-shifting winding, and a shunting tap of a high-voltage-side long-side terminal is serially connected with an opposite adjacent-phase short-side terminal via a tap switch, so that a closed phase-shifting loop is formed; shunting taps at the terminals of the windings are serially connected via tap switches to achieve switching voltage regulation; the low-voltage-side windings in star connection and in angular connection output multi-pulse electric energy definite in phase-shifting angle and regulatable in voltage to a rectifier. The phase-shifting winding type voltage-regulating rectifier transformer and the voltage regulating method thereof have the advantages that phase-shifting angles are definite, voltage regulating range and the number of winding tapping turns are matched well, and the voltage-regulating rectifier transformer is compact in structure and good in manufacturability, so that manufacturing cost and operating loss of the transformer are reduced.