The invention provides a controlled reactor-based series voltage control device of a circuit, which comprises a three-phase transformer XB, and a three-phase series voltage control circuit consisting of single-phase transformers XCA, XCB and XCC, controlled reactors LBA, LBB, LBC, LCA, LCB and LCC and capacitors CA, CB and CC. The series voltage provided for the circuit by the device can be equivalent to the supraposition of two voltage components, wherein one component is parallel to a secondary side voltage vector of the three-phase transformer XB; while the other component is vertical to a circuit current vector. In an effective control range, the series voltage control device of the circuit converts any three-phase symmetric alternating current into the alternating current which has the same frequency and has amplitude and a phase meeting requirements directly, and connects the converted alternating current into the circuit in series so as to realize discontinuous adjustment of the amplitude and the phase of the series voltage of the circuit.