To reduce temperature measurement error caused by the wavelength-related loss of Raman scattering light and extra noise of photodetector and Rayleigh noise in scattering lights of the Raman-distributed temperature sensor system, an anti-Stokes optical noise reduction method developed by analyzing the demodulation principle of distributed optical fiber temperature-sensing system in this paper. The optical fiber is laid according to the ring structure. The average value of the base noise following the Fresnel reflection peak in each measured anti-Stokes optical signal is taken as the dynamic background noise. Two sections of the optical fiber at different temperatures are used to eliminate the Rayleigh noise after the dynamic background noise. In theory, the anti-Stokes light noise reduction demodulation method prevents the temperature measurement error introduced by the reference Stokes light and eliminates the temperature measurement error caused by background noise and Rayleigh noise. The experimental results demonstrate that the maximum temperature measurement error of the modified distributed optical fiber temperature-sensing system is decreased from 5.4 ℃ to 0.6 ℃, and the temperature measurement accuracy is significantly improved.