The invention provides a line voltage regulating transformer with a vector transformation function. The voltage regulating transformer comprises a vector transformation coil set, voltage regulating coils and voltage regulating iron cores. The voltage regulating coils are installed on the voltage regulating iron cores, and the two sets of voltage regulating coils and voltage regulating iron cores are installed on each voltage regulating transformer. The vector transformation coil set comprises two coils, and the two coils are coaxially wound outside the two sets of voltage regulating coils andvoltage regulating iron cores, so that the two sets of voltage regulating coils become vector iron cores simultaneously. The line voltage regulating transformer is installed in the middle section of aline, conducts transformation through a vector phase and is used for solving the problem that a country low-voltage system single-phase transmission voltage is low; the vector coils and an iron corestructure are designed, and a double-phase voltage of 380 V and with a phase angle of 120 degrees free of zero lines is transformed into a phase-free single-phase voltage (vector transformation); a voltage regulating coil structure is designed, and the voltage subjected to the vector transformation is automatically raised to the voltage range needed by a user on line. The low voltage problem, caused by the problems of a tail end load and the line diameter, of an already built line is solved.