Abstract: A reflection polarization maintain optical fiber temperature sensor was proposed based on the polarization mode interference theory in polarization maintain optical fiber and the sensing equation was derived. Analyses prove this sensor can achieves high accuracy and the measurement range can be adjusted easily by changing the polarization maintaining optical fiber sense probe length. For the demand of field temperature monitoring of huge power transformers, a prototype with special high temperature polarization maintain optical fiber sensing probe and sealed package was made and the sensor probe can stand the harsh environment of hot oil and high voltage. With this prototype, the temperature within range 0℃~180℃ was measured and the linear output was obtained after model linearized and date processed. Long time measurement was investigated in 0℃ environment formed with mixer of ice and water, the result shows the sensor stability and accuracy were both better than 0.15℃.