A ring cavity fiber laser based on the filter of up-tapered Mach-Zehnder interferometer(MZI) was proposed and demonstrated for displacement sensor experimentally. The up-tapered MZI was easily fabricated by using a commercial fusion splicer. The peak wavelength of the laser bule-shifted with the different bending direction by decreasing the distance between the two stages. The maximum sensitivity of 4.49 nm/mm and extinction ratio of more than 50 dB were achieved. The configuration of up-tapers were strong in strength, therefore, the bending radius of the whole fiber were almost the same. Note that this kind of configuration is easy in fabrication and low in cost which is beneficial for engineering application.