Abstract: A new method of using optical fiber sensors to measure tiny displacement of high-speed rotating component was proposed to realize the non-contact high speed and high precision displacement measurement. On the base of measurement principle of optical fiber sensors, relation between light intensive and range was calculated in this paper. Voltage fitting formula between business value and range was established by turning a light intensity into a voltage signal. Test bench for measuring the parameters of V belt was designed to measure the radial displacement of V belt when stable operating in race to get the knowledge of track of V belt in belt pulley and the slide angles. New sliding angle formula was drawn by continuous optimizing the original V belt sliding angle. Comparative results from two experiments show that the new formula is more accordance with experiment with less error and can provide theoretical basis for the accurate design for V belt.