Abstract: To enhance the integration of terahertz transceivers and reduce the size, a 220 GHz fundamental mixier based on ground coplanar waveguide(GCPW)GaAs circuit is designed and fabricated. At first, the I-V and C-V curves of the GaAs Schottky diode are measured, then the parasitic parameters of the Schottky diode are determined. The Schottky diode, filter, and 3 dB couplerare are designed individually and simulated jointly, achieving a 220 GHz mixer circuit.By optimizing the integration process, the diode is flip-chip bonded to the circuit, facilitating the GaAs mixer circuit. The measured result shows that under the condition of a fixed intermediate frequency of 5 GHz, the conversion loss is better than 15 dB in the frequency range of 200 GHz~220 GHz and the minimum conversion loss is 10.6 dB at 204 GHz.The GaAs circuit on GCPW is simple, eliminating the need for waveguide cavity assembly. It can be integrated with other radio frequency devices to reduce the volume.