In this paper, we propose a dual-polarization ultra-wideband metasurface with half-reflection and half-transmission based on a double-split-ring (DSR) structure operating in a terahertz (THz) frequency range. The designed metasurface can simultaneously control the circularly polarized (CP) wave and linearly polarized (LP) wave in reflection mode and transmission mode, covering an extensive THz frequency range. The unit-cell architecture of the metasurface consists of a periodic arrangement of the DSR structure made of metal, which is affixed to an ultra-thin dielectric substrate. By manipulating the size and rotation direction of the DSR structure, we achieve full phase coverage of 0–2π of the orthogonally polarized LP wave and CP wave across a frequency span of 0.3–1.2 THz, encompassing transmission and reflection scenarios. The relative bandwidths of the corresponding orthogonal LP wave and CP wave with an average amplitude of 0.45 reach 86% and 120%, respectively. Specifically, through numerical simulations, we demonstrate that the designed metasurface has the ability to achieve THz beam deflection and vortex beam generation while reflecting and transmitting LP wave and CP wave. The proposed dual-polarization ultra-wideband metasurface holds great promise for various applications in the terahertz frequency range. These findings pave the way for the development of flexible and versatile THz devices with expanded functionality, thereby opening up new possibilities for wavefront manipulation in metasurfaces.