A kind of fiber optical temperature variety sensor based on fiber optical ring resonator is presented. The temperature variety causes the variety of the round-trip phase of the ring and the movement of the resonance dips. The magnitude and rate of the movement are proportional to the magnitude and rate of temperature variety, respectively. Through the measurement of the dips movement, the temperature variety can be sensed. In this paper, we make a theoretic analysis about the sensor, propose the system configuration, present a simple and effective signal detection method, and analyze the performance of the sensor. This kind of temperature sensor has such characteristics as high sensitivity, simple detection method, flexibly changeable sensitivity for different applications and temperature variety detection. Combined with the multiplex technology such as time division multiplexing (TDM), the sensor can form temperature variety sensor array for distributed fiber optic temperature detection.