Summary: The characteristics of a highly sensitive terahertz wave detector based on lithium niobate have been investigated using a steady-state theory. The contributions of the low-frequency modes to the dielectric constant of lithium niobate are considered. The intrinsic factors of the LN detector limit its high frequency response to about 4 THz. Temperature dependence of the detector from room temperature to \(250^\circ C\) was also studied. The main factors associated with the temperature variations of the sensitivity of the detector are thermal expansion, the nonlinear coefficient and the refractive index of the crystal. The nonlinear coefficient dominates the temperature dependence of the sensitivity of the detector, while the impact of the refractive indices of the near-infrared lights on the temperature variation of the sensitivity of the detector is negligible. This study provides a useful guide and a theoretical basis for the further improvement of the detection systems.