The optical fiber sensing system is provided. The optical fiber sensing system comprises an optical fiber measuring module, a floating module, and a containing structure. The floating module disposed in the containing structure has a plurality of floating units. Each floating unit has a mass element and a vibration absorbing structure. It is adapted to apply appropriate tensile force to the optical fiber measuring module by adjusting counterweight of the quality bodies. The vibrating influence to the optical fiber measuring system would be reduced through the vibration absorbing structure.