Abstract: Aiming to reduce the noise of terahertz receiver advance dramatically, a method which is used to design low-noise terahertz sub-harmonic mixer based on Schottky diode is presented. After obtaining the accurate 3D model and electrical model of the schottky diode, the impact hammer-head filter structure and low loss quartz glass integrate circuit is adopted to design 340GHz and 250 GHz terahertz sub-harmonic mixer. The measured result indicates that the lowest double sideband conversion loss and the lowest noise temperature of the 220 GHz sub-harmonic mixer is below 6.5dB and 650K respectively within 205～235GHz band. And the corresponding measured result is below 6.5 dB and 900K for 250 GHz mixer across 230～270GHz.