The invention discloses a series voltage injection-based current-type high voltage direct current transmission (LCC-HVDC) system commutation failure suppression method. The core of the method is thatthree-phase voltage series injection is carried out between the inverter of the LCC-HVDC and a receiving-end AC system to compensate dynamic fall of the voltage of the receiving-end AC system, seriesvoltage injection is realized through a unified power flow controller, a parallel transformer of the unified power flow controller is parallelly connected at the AC system side, and a series transformer is serially connected at the inverter side of the LCC-HVDC. A dynamic voltage series injection control algorithm is designed for the series converter of the unified power flow controller, so as toenable the three-phase voltage generated by the series converter of the unified power flow controller to dynamically compensate the dynamic fall of the voltage at the AC system side through the seriestransformer. Voltage distortion and voltage fall at the LCC-HVDC inverter side can be further reduced, and finally, the LCC-HVDC inverter commutation failure possibility is reduced.