In view of cross sensitivity of the high-precision frequency-modulated continuous-wave fiber optic pressure sensor to temperature and pressure, the temperature characteristics of the pressure sensor are analyzed theoretically and experimentally. The structure of the pressure sensor is optimized, the effect of temperature on Fabry-Perot (F-P) cavity can be reduced to 50 μm. After theoretical calculations, it can be known when the temperature changes from 25 ℃ to 65 ℃, the deformation of the F-P cavity by the temperature is 1000 μm. By optimizing the F-P cavity design, the influence of temperature on the length of the F-P cavity can be effectively reduced. The relationship between the deformation of the cavity length of the optimized F-P cavity and the temperature is tested through experiments. The least-squares method is used for temperature compensation in real-time. After the temperature compensation, the deformation of the F-P cavity length is directly reduced from 50 to 4.5 μm, which reduces temperature cross-sensitivity, improves the reliability and practicability of high-precision frequency-modulated continuous-wave fiber optic pressure sensing measurement.