A single-stage three-phase AC-DC converter is presented in this paper. The front semi-stage of the proposed converter, which is operated in discontinuous conduction mode (DCM), is utilized for power factor correction and the rear semi-stage of the proposed converter, which is operated in continuous conduction mode (CCM) at heavy loads and in DCM at light loads, is employed for step-down voltage conversion. The proposed converter can achieve almost unity power factor, low total harmonic distortion of input current (THDi), and adjustable DC output voltage. The voltage stress across the DC-link capacitor is low. Moreover, the steady-state analyses of voltage gain and the boundary operating condition are discussed. Finally, experimental results are provided to verify theoretical analyses.