A Mach-Zehnder interferometer (MZI) based on thin-core fiber is experimen tally demonstrated and used for measurement of temperature,strain,surrounding refractive index and bending.Th e thin-core fiber (TCF) was sandwiched between two single mode fibers (SMFs) through two waist-enlarged bit apers to form an MZI.Due to the core diameter mismatching between the two fibers ,cladding modes are excited at the first splicing point and then coupled into the fiber core at the second splicing point to generate interference. Wavelength shift of the interference fringes was used to measure the change of a mbient parameters.Since the core of the TCF contains Germania with mode percent of 38%,it has a relatively h igher differential refractive index and higher thermal-optic coefficient compared with normal fibers.As a result,by ensuring an appropriate free spectral range (FSR),relatively short length of sensing fiber (2mm) an d relatively higher temperature sensitivity can be expected. Experimental results show that the temperature sensitivity is up to 70.2pm/℃ i n a range from 30℃ to 250℃.The sensor responses to refractive index,strain and bending were also measured,and the achieved sensitivities are －8.12nm/RIU,1.8pm/με and 2.07nm/m－1, respectively.