After comparing wide-band antenna and narrow-band antenna, a dual-frequency Terahertz antenna for wireless communication was designed. It consisted of two dipole antennas which are located on two different layers and arranged vertically to avoid connection and interaction. The two dipoles both had THz chokes to improve performance, and different sizes to operate in two different frequencies. The upper dipole use metal probe to connect the LT-GaAs substrate through the hole of substrate, and share the same photomixer with the lower dipole. The photomixer can be lighted by the same light for pumping, while the two dipole can be controlled by different circuit for bias. So they can work at different frequency and vertical direction of polarizations. They can adjust for the air’s low-loss frequency by changing the size. The dual-frequency antenna had high performance because of containing two dipole antennas. At the air’s low-loss frequency of 0.21THz, 0.35 THz, 0.41 THz, 0.68 THz, 0.85 THz and 0.93 THz, it had total efficiencies of 14.9%, 28.4%, 33.9%, 28.4% and 21.6% respectively, and max realized gain of 2.99 dB, 10.6 dB, 11.8 dB, 18.4dB, 18.2 dB and 18.3 dB respectively.