This paper presents a novel approach to achieve both tight dc voltage regulation and direct power factor control by applying G-SVM (General Direct Space Vector Modulation) of matrix converter theory to three-phase ac-dc matrix rectifier. The reduced form of G-SVM and the derivation of the three-phase ac-dc matrix rectifier from three-phase ac-ac matrix converter are described and theoretically justified. The proposed matrix converter features intrinsic buck conversion, tight output voltage regulation via modulation, inherent capability of four-quadrant operation, elimination of the bulky storage component on the dc bus and sinusoidal input current. Moreover, the reduced G-SVM controlled three-phase ac-dc matrix rectifier can achieve leading, lagging or unity input power factor by simple and direct control of the input current displacement angle. This significantly benefits the potential application of the reduced G-SVM controlled three-phase matrix rectifier to automotive, aircraft, ship, and other three-phase standby dc supplies. In these applications, the unity power factor control is indispensable when the dc load changes widely. Simulated and experimental verification for this strategy has been presented and discussed in this paper.