For the real-time detection of liquid temperature in special environments such as strong magnetism and small spaces， a reflective fiber-optic temperature sensor for real-time detection of liquid temperature is designed. The sensor makes use of the law that the refractive index of a liquid changes with temperature and combines the characteristics of light propagation in a liquid. Based on the rule of liquid refractive index changing with temperature， the temperature measurement principle of reflective optical fiber temperature sensor is proposed； According to the temperature measurement principle of the reflective optical fiber sensor， the sensor probe structure is determined. The mathematical model of the sensor is established based on the characteristics of the approximate Gaussian distribution of the optical fiber's fiber end light field. The influence of different parameters on the sensor output characteristics is analyzed. The experimental platform of the sensor is set up and static calibration is performed. The experimental results show that within the measurement range of 30 ~ 120 ℃ the sensor can detect the temperature with a sensitivity of 0.71 mV /℃.