伴随着6G 通信的发展，雷达遥感、检测成像等多个领域向太赫兹频段拓展，获取材料在该频段的介电常数显得愈发重要。本文基于NR 迭代法提取了太赫兹频率下样品的复介电常数，分析了迭代法的初值选取对提取结果的影响。在325~500 GHz 频段(Y 频段)搭建了一套由矢量网络分析仪(VNA)、扩频模块和四抛物面镜组成的8f 准光系统，实现散射参数S 2 1 的自由空间测量。由电磁波传输模型推导出复介电常数与S 2 1 之间的关系式， 利用迭代法提取出了特氟龙(Teflon)、丙烯腈-丁二烯-苯乙烯共聚物(ABS)和聚甲基丙烯酸甲酯(PMMA)样品的复介电常数谱，与其他文献报道的结果一致，验证了系统和方法的有效性。

It is important to obtain the dielectric constant of materials in terahertz band for applications of 6G communication, radar remote sensing, detection and imaging. In this paper, the complex permittivity of samples is extracted based on the Newton Raphson(NR) iterative method, of which the influence of the initial value is analyzed. A set of 8f quasi optical system consisting of Vector Network Analyzer(VNA), spread spectrum module and four parabolic mirrors is built in 325~500 GHz(Yband) to realize the free space measurement of scattering parameter S 21. The relationship between complex permittivity and S 21 is derived from the electromagnetic wave transmission model. The complex permittivity spectra of Teflon, ABS and PMMA samples are extracted by iterative method. The results are consistent with other literatures, which verify the effectiveness of the proposed system and the method.