A Raman fiber temperature sensing system based on sample-ring aualanche photo diode (APD) gain adjusting and temperature calibrating method is proposed and experimentally demonstrated. The proposed system controls the APD bias by comparing the deviation of signal line and baseline obtained from the sample- ring, maintaining a substantially constant APD gain, thus ensuring temperature measurement accuracy and signal to noise ratio. Signal line obtained from the sample-ring is also used as reference signal for temperature calibration, further eliminating measured errors caused by inevitable APD gain fluctuation due to uncertain factors. Experimental results show that the proposed method significantly improves system performs in signal to noise ratio, stability and temperature measurement accuracy with respect to conventional Raman fiber temperature sensing system, it has practical value.