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 potential for applications. At present, software is mainly used to simulate and analyze the structures relied upon for semiconductor terahertz detection of bulk materials, while the simulation analysis for terahertz detection in low-dimensional material systems is still relatively unexplored. Due to the low degrees of freedom in carrier motion in low-dimensional materials, the probability of scattering caused by collisions between electrons and the lattice in the channel during electron movement is effectively reduced, making these materials have 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 work simulates and analyzes the plasmon wave effect in a monolayer MoS₂ field-effect transistor (FET) for THz detection for the first time, and systematically elucidates the principle and analysis process of using plasmon waves for THz detection. The transmission characteristic curve of the device is simulated and measured at a source-drain voltage of 0.5 V, and, a gate-to-drain voltage of –0.1 V is selected based on this curve to preliminarily investigate the THz response performance of the device. By adjusting key parameters such as U_gs, THz wave irradiation frequency, and HfO₂ layer thickness, it is found that the monolayer MoS₂ FET THz detector can produce a maximum DC voltage signal of 14 μV. This signal exhibits a complex variation trend related to the bias voltage between the gate and drain. This trend correlates with the bias voltage-induced changes in carrier concentration and the corresponding momentum relaxation time. The research results obtained in this paper can provide an important reference for designing low-dimensional material THz detectors. Furthermore, they lay a foundation for optimizing the performance of two-dimensional material THz detectors through simulation analysis, thereby providing deeper insights into the study of THz photoelectric responses in 2D materials.