The backscattering characteristics of optical microfiber (OM) are experimentally studied by controlling heating temperature and cooling method during the OM fabrication process. OM samples with various reflectances from 0.1% to 1% are achieved. An OM with waist length of 5 mm, waist diameter of 1 \mu m, and approximately 0.5% reflectance is used as the end reflector of a fiber Fabry-Perol (F-P) interferometer. A piezoelectric ceramic transducer (PZT) fiber phase modulator is used to test the sensing performance of the fiber F-P interferometer. Experimental results verify that the OM with low reflectance can be used as a reflector in the F-P interferometer.