Abstract: Thermal analysis of LiTaO3 film infrared detector based on ANSYS has been studied in this paper. The influences on the thermal analysis results are obtained, through changing the substrate material and its thickness and the thickness and thermal conductivity of thermal-insulation layer of the LiTaO3 film infrare sensing element. The thermal response of the infrared detector increases with the thickness of thermal-insulation layer but is in inverse proportion to its thermal conductivity. Among the substrate materials of silicon, nickel, and sapphire, the LiTaO3 thin film infrared detector with sapphire substrate has the best thermal response. The influence of the thickness of substrate can be ignored when the infrared detector with 2 μm thick thermal-insulation layer. An optimized model is presented and the comparing simulation results of the optimized and the original are given out. The experiment result verifies the validity of the optimized model.