A novel micro-mechanical temperature sensor is presented theoretically and experimentally. The working principle of this sensor is based on Optical interference theory of Fabry-Perot cavity that is formed between a polished optical fiber end and micro-mechanical Bi-layered membranes. When ambient temperature is changing, Bi-layered membranes will be deflected based on 'Bi-coating effect', and then the length of Fabry-Perot cavity will be changed correspondingly. By detecting the optical output of Fabry-Perot cavity resulted from the change of Fabry-Perot cavity length, the ambient temperature can be measured. First, using finite element software ANSYS, the structures of this sensor was designed and corresponding theoretical model was set up based on theoretical analysis; Second, the sensor structure was optimized based on Fabry-Perot optical Interference theory and Bi-layered membranes dimensions selection, and theoretical characteristics was given by simulation; Third, using optical fiber 2×2 coupler and photo-electrical detector, the fabricated sample sensor was tested successfully by experiment that demonstrating above theoretical analysis and simulation results. This sensor has some favorable features, such as: micro size owing to its micro-mechanical structure, high sensitivity owing to its working Fabry-Perot interference cavity structure, and optical integration character by using optical fiber techniques.