The configurations of a three-phase buck-boost power factor correction (PFC) circuit and a controlling method thereof are provided in the present invention. The proposed circuit includes a first single-phase buck-boost PFC circuit receiving a first phase voltage and having a first and a second output terminals and a neutral-point for outputting a first and a second output voltages, a second single-phase buck-boost PFC circuit receiving a second phase voltage and coupled to the first and the second output terminals and the neutral-point, a third single-phase buck-boost PFC circuit receiving a third phase voltage and coupled to the first and the second output terminals and the neutral-point, a first and a second output capacitors coupled to the first and the second output terminals respectively, and to the neutral-point also and a neutral line coupled to the neutral-point.