Abstract: An optical fiber displacementvibration sensor using the incoherent light as a light source and the mirror as a reflective surface was analyzed. The analytic expressions of the optical fiber output power and the measurement distance were derived.The relationship between power ratio and measurement distance was detailedly investigated based on different optical fiber radii, different numerical apertures, different spacings and included angles between transmitting and receiving optical fibers.The results of numerical simulation show that the measurement precision and scope are affected by the optical fiber radius,the optical fiber numerical aperture, the distance and axis angle of both transmitting and receiving optical fibers. By analyzing the variation curves of distance and output power ratio, it is helpful to select the appropriate sensor according to the measurement target in practical engineering applications. Moreover, the measurement error was discussed. The results shows that the measuring range of distance is increased with the increasing of optic fiber included angle, while the error rate is reduced.The error rate is 1% for the included angle of 0.25.