A refractive index and temperature sensor is proposed based on tapered triple cladding quartz specialty fiber (TTCQSF). The SMF-TTCQSF-SMF structure is fabricated by drawing a section of fused TCQSF which is spliced in the both ends with two single mode fibers (SMFs). Then an in-fiber Mach-Zehnder interferometer (MZI) is achieved. The optical path difference between the fiber core mode and cladding mode of TTCQSF can vary with the changes of the external environment. And it causes the change of the sensor interference spectrum. Monitoring the variation of the transmission spectrum can determine the ambient physical parameters. The sensing performances of refractive index and temperature of the sensor are tested, respectively. The experimental results show that the transmission spectra of the sensor have red shift when the refractive index increases in the range from 1.3350 to 1.3466 and have blue shift when the temperature increases in the range from 25.7 ℃ to 94.9 ℃ . The refractive index sensitivity is 1673.94 nm/RIU and the temperature sensitivity is -0.061 nm/℃, where RIU is refractive index unit. Both of them have good linearities. The sensor has the advantages of easy manufacturing and high sensitivity. So it has a good application prospect in the fields of refractive index and temperature measurement, such as biochemistry and industrial production.