Abstract: By combining ends of a multimode fiber with a length of 17 mm and single-mode fiber(SMF), multimode fiber is then subjected to a tapered treatment to obtain a tapered multimode fiber with a wavelength and intensity sensor. Temperature sensing characteristics of sensor in range of 30 ℃ ~ 80 ℃ were studied experimentally. Experimental results show that when ambient temperature changes, response sensitivity of sensor to temperature of interference trough near 1 542 nm can reach 0. 041 nm / ℃ and 0. 106 dB / ℃ respectively, and there is a good linear relationship between wavelength response and intensity response of sensor interference fringe. Based on this linear relationship between sensor wavelength response and intensity response, phase demodulation of interferometric fiber optic sensor can be realized by detecting intensity of sensor signal. This method provides a new idea for sensing and demodulating signal value.