A kind of infiber MachZehnder interferometer based on fiber taper was proposed. The sensor is formed by cascaded two fusion tapers in singlemode fiber through a fusion splicer. The fiber taper has a diameter of 43.7 μm and length of 480 μm. The fiber taper acts as couplers, it could not only excite the highorder modes, but also couple these modes into singlemode fiber to form the intermodal interference. When surrounding refractive index and temperature of the surrounding liquid changes, the intermodal phase difference changes. Through monitoring the transmission spectrum of the interferometer, the refractive index and temperature were determined. The experimental results show that the sensor sensitivity is －128.33 nm/RIU in the RI range of 1.335~1.403RIU, and the temperature sensitivity is 0.111nm/℃ in the water temperature range of 30~75℃. The sensor has advantages of easy fabrication, high sensitivity, and inexpensive, which has a potential in biological sensing.