The invention provides a unified power flow controller with multiple operational modes. The unified power flow controller comprises a transformer, a converter module (12) and a mode conversion switch module (11), wherein the transformer comprises at least one series transformer (3) connected to a power transmission line in series and a shunt transformer (8) connected to an alternating current system in parallel; and one end of the converter module (12) is connected with the shunt transformer (8) through the mode conversion switch module (11) while the other end of the converter module (12) is connected with the corresponding series transformer (3) through the mode conversion switch module (11). When the unified power flow controller is used for the power transmission line or the power distribution line, the power flow control capability and the voltage stability of the line can be greatly improved, so that the unified power flow controller has the advantages of flexible function and high reliability.