The invention discloses a Q-band ultra wideband half-plane terminal antenna. The antenna is of a plane structure, comprising a dielectric substrate, a double dipole oscillator which is arranged on the dielectric substrate as a radiating unit, a feed network for energy distribution, an equivalent SIW (Substrate Integrated Waveguide) semi-opened cavity through which the half-plane radiation of the antenna can be achieved and the beam width can be controlled, and a plurality of metallic through holes formed in the dielectric substrate; the SIW semi-opened cavity can be also used for adapting the antenna to the SIW while considering the balun, electrostatic shielding and wideband matching effect. In light of the development demand of terminal antennas, the antenna is small in non-circularity, high in efficiency, and ultra-wide in band, the beam width is easily controlled, and the integration is easily carried out.