An up-tapered fiber strain sensor based on Mach-Zehnder interferometer(MZI) was proposed and demonstrated. With the MZI as a filter, the laser was finally generated in the optical fiber ring resonator through comb filtering at the gain spectrum of erbium-doped fiber. The MZI could work as filter as well as carry on the sensor of optical fiber axial strain, and thus realize the output wavelength of the laser blue-shifts with the increase of strain. The experiment result shows that the sensor around the wavelength of 1 557 nm exhibits the axial strain sensitivity of 3 pm/με by monitoring the wavelength shift. Moreover, the up-tapered MZI fabrication process is very simple, cost effective and high mechanical strength.