A high sensitivity optical fiber temperature sensor based on Mach-Zehnder interferometer(MZI) and dimethyl silicone oil(DSO) is introduced in this paper. The sensor consists of MZI and DSO filled on its surface. The MZI consists of single-mode fiber-tapered no-core fiber-single-mode fiber. After the DSO is filled, the resonant peak of MZI shifts a little to the right. The ambient temperature is measured by tracking the change of MZI resonant peak wavelength with temperature. The temperature sensitivity of the sensor is -97.7 pm/℃, while the temperature sensitivity of MZI without DSO is -50.1 pm/℃. The sensitivity of the sensor is increased by about 1.95 times. The sensor has the advantages of simple structure, easy fabrication, low cost and high sensitivity, and has a certain application prospects.