Low-dimensional material systems benefit from their extremely high carrier mobility and flexible integrability, making them a subject of research in the terahertz detection field and demonstrating significant application potential. Currently, the structures relied upon for simulation and analysis of semiconductor terahertz detection using software primarily target bulk materials, while simulation analysis for terahertz detection in low-dimensional material systems remains relatively unexplored. Due to the low degrees of freedom in carrier motion within low-dimensional materials, the probability of scattering caused by collisions between electrons and the lattice in the channel during electron movement is effectively reduced, endowing these materials with immense potential in high-sensitivity detection. Their low equivalent noise power and high signal-to-noise ratio performance in signal detection highlight the broad development prospects of these materials in the field of communication. This paper presents, for the first time, a simulation analysis of plasmon wave effects in a monolayer MoS₂ field-effect transistor (FET) for THz detection, systematically elucidating the principles and analytical processes of THz detection utilizing plasmon waves. The simulation measured the transfer characteristic curve of the device at a source-drain voltage of 0.5 V, and based on this curve, a gate-to-drain voltage of -0.1 V was selected for preliminary investigation of the device's THz response performance. By adjusting key parameters such as U_gs, THz wave irradiation frequency, and HfO₂ layer thickness, it was determined that the monolayer MoS₂ FET THz detector could output a maximum DC voltage signal of 14 μV. This signal exhibits a complex variation trend with the bias voltage between the gate and drain, which is correlated with the bias voltage-induced changes in carrier concentration and the corresponding momentum relaxation time. The research conducted in this paper can serve as an important reference for designing low-dimensional material THz detectors. Furthermore, it provides a foundation for optimizing the performance of two-dimensional material THz detectors through simulation analysis, thereby offering deeper insights into the study of THz photoelectric responses in 2D materials.