A high-sensitivity temperature sensor based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The shift of the oscillation frequency in the OEO is inversely proportional to the variation of temperature. An injection-locking method is employed to set up the initial oscillation frequency of the sensor to overcome the uncertainty of the initial oscillation frequency. The experiment results show that high sensitivity of 43.91 kHz/°C with an accuracy of ±0.12°C is achieved between 20°C and 240°C. The system features high temperature sensitivity, wide dynamic range, and high reliability.