随着通信技术的飞速发展，传统微电子行业出现瓶颈，人们更多地寄希望于集成光路来实现新的突破。硅基光子学因其自身材料以及制造工艺等方面的优点而备受关注。其中，硅基耦合器作为重要的硅基无源器件，是实现光的片上合束和分束的关键。多模干涉（multimode interference, MMI）耦合器具有损耗低，工艺容差性大且带宽较大等优点，是一种常用的集成光学器件。从MMI耦合器的自映像成像原理出发，利用导模传输分析法（guide-mode propagation analysis, G-MPA）对MMI中的模场分布情况进行分析，成功设计出基于470 μm高阻硅晶圆的太赫兹波段的taper型多模干涉耦合器。通过时域有限差分法（finite difference time domain method, FDTD）仿真优化其参数，实现了93.8%的耦合效率。“,”With the rapid development of communication technology, the bottleneck appears in the traditional microelectronics industry. More and more people hope that integrated optical circuit can achieve new breakthroughs. Silicon photonics has attracted much attention because of its advantages in materials and manufacturing technology. Among them, the silicon coupler, as an important silicon passive device, is the key to achieve beam coupling and beam splitting on chip. Multimode interference (MMI) couplers are commonly used as integrated optical devices because of their advantages such as low loss, large process tolerance and large bandwidth. In this paper, based on the self-imaging principle of MMI, guided mode propagation analysis (G-MPA) is used to analyze the mode field distribution in MMI, and a taper multimode interference coupler based on 470 μm high resistance silicon wafer in terahertz band is successfully designed. The coupling efficiency of 93.8% is achieved by FDTD simulation and optimization of its parameters.