A scheme for vector terahertz (THz) beam generation is proposed. A subwavelength metal grating is utilized to adjust the polarization of the THz radiation. The amplitude and phase distributions of the THz beam are dynamically regulated by a THz computer-generated hologram (CGH) pattern of the photo-generated carriers. A radially polarized THz beam and a vector THz vortex beam with a topological charge of 1 are generated to demonstrate the validity and the effectiveness of the proposed scheme. Experimental results correspond to the theoretical simulations well. Moreover, the proposed method is applicative for a broadband THz radiation. These results could be applied in the THz sensing, THz imaging, and THz communication in the future.