To eliminate the measurement errors caused by fiber loss and loss variations, a solution employed in Raman distributed fiber sensing system with fiber-ring calibration method and double-ended injection structure is proposed and experimentally demonstrated. Double-ended injection structure adopted in the system eliminates the influence ofwavelength-dependent loss and local loss through geometric mean of anti-Stokes Raman scattering signal timesharing obtained from both ends of the sensing fiber. The fiber-ring calibration method is used to correct measurement errors caused by real-time variations of fiber losses. Moreover, with instantaneous switch between double-ended injection structure and single-ended mode, the system can monitor the temperature of the entire fiber even with presence of break point. Experiments show that measurement accuracy of 0.9 ℃ is obtained within temperature range of 15 ℃~210 ℃.