A fiber sensor based on Mach-Zechnder interference (MZI) for measuring tem perature is proposed in this paper.The temperature fiber sensor is constructed by a polariza tion maintaining fiber (PMF) between two conventional single-mode fibers (SMFs) and based on concatenated down and up-tapers simply fabricated by arc discharging and fusion splicing.B y observing the wavelength and intensity shifts of different interference dips,temperature c an be measured, since the core modes and the cladding modes have different sensitivities to temp erature. Experimental results indicate that when the temperature is from 25℃ to 70℃, for the 30mm PMF sensor,wavelength sensitivities of the wavelength dips at 1533.68nm and 1560.92nm are 0.029nm/℃ and 0.040nm/℃,and the intensity sensitivities are 0.12dB/℃ and 0.097dB/℃;for the 40mm PMF sensor, wavelength sensitivities of the wavelength dips at 1540.54nm and 1568.64nm are 0.0835nm/℃ and 0.0998nm/℃,and the intensity sensitivities are 0.152dB/℃ and －0.211dB/℃.For the spectrometer with a wavelength and intensity distinguishability of 0.01nm and 0.01dB,the proposed fiber sensor can reach the distinguishability of 0.100℃ and 0.047℃ for wavelength and int ensity,respectively.