Abstract: To meet non-reciprocal requirements of full-space multifunctional electromagnetic (EM) devices, a full-space digital coding metasurface is proposed at Ku band. The meta-atom consists of five metal layers. Therein, rectangular patches on layer 1 and 5 are perpendicular to each other, controlling the phase of forward (along −z) x-polarized and backward (along +z) y-polarized EM waves, respectively. Their adjacent grating structures act as metal grand to ensure nearly 100% reflectivity. Layer 3 is an open rectangular resonant ring, a high polarization convertion rate and purity can be achieved under forward y-polarized and backward x-polarized channels with orthogonal grating structures on its both sides. It also can achieve 360° phase control by changing rotation angle and size of resonant ring. Here, 3-bit phase encoding is adopted and three independent EM functions (Function I: triple pencil beams generation, Function II: trifocal lens, and Function III: four vortex beams generation) are achieved in forward and backward transreflective space based on the principle of complex phase addition. The designed multifunctional metasurface with polarization and direction multiplexing improves the channel capacity and utilization efficiency of space EM waves, which has a broad application prospect in the fields of multichannel communication, transreflective radome, and multi-target detection.