A fiber sensor based on Mach-Zechnder interferometer (MZI) for simultaneous measurement of temperature and strain is proposed in this paper.The fiber sensor is constructed by sandwiching a thin core fiber between two spherical-shaped fibers.By observing the wavelength shifts of different interference dips and using the sensitivity matrix,temperature and st rain can be measured simultaneously,since the core modes and the cladding modes have differe nt sensitivities to these two external parameters.The wavelength dips at 1545.1nm and 1554.8nm are chosen.Experimental results indicate that the temperature sensitivities of t he dips are 53.86pm/℃ and 47.51pm/℃,and the strain sensitivities of the dips are 0.75pm/με and 1. 39pm/με,respectively.The linearity of the experiment results is good.