A temperature sensor using spherical-shaped fibers based on the March -Zehnder interference is proposed.The proposed fiber optic sensor ca n be achieved by cascading two spherical-shaped single mode fiber (SMF) structures.The effective refractive in dex of the cladding mode changes with the external temperature,and then the interference transmission sp ectra change accordingly.By observing the wavelength shifts of the interference dip,tempera ture can be measured. Experimental results show that when the temperature changes from 18℃ to 78℃, the sensitivity is 0.1297nm/℃ when the spacing of the two spherical-shaped structures is 1.8cm.And wh en the spacing is 2.4cm,the sensitivity is 0.1214nm/℃.When the spacing is 2.4cm,the sensitivity is 0.0704nm/℃. According to the wavelength resolution of 0.01nm,the sensor can achieve a resolution of 0.0771℃. The temperature sensor based on spherical-shaped fibers has many advantages,in cluding high sensitivity,compact,simple and low cost.Therefore,it has great pote ntial for measurement of temperature.