The creep properties of optical fiber used in fiber optical sensors were studied in this paper. A low co- herent white light double interferometer system was designed and calibrated and the creep deforma- tions of optical fibers under static and cyclic loadings were measured with this device. The research results showed that polymer coated optical fibers crept at the beginning when they were under static or cyclic load. As the number of the cyclic loading or the static loading times increased the creep tended to stop. Thus to ensure that the optical fiber keeps pre-stress for long time in pressure transducer, it is recommended that the optical fiber should be tensioned cyclically before being fixed into the sensor device. The creep properties of optical fiber used in fiber optical sensors were studied in this paper. A low co-herent white light double interferometer system was designed and calibrated and the creep deforma- tions of optical fibers under static and cyclic loadings were measured with this device The research results showed that polymer coated optical fibers crept at the beginning when they were under static or cyclic load. As the number of the cyclic loading or the static loading times increased creep tended to stop. Thus to ensure that the the optical fiber keeps pre-stress for long time in pressure transducer, it is recommended that the optical fiber should be tensioned cyclically before being fixed into the sensor device.