The invention relates to a device for lowering the PMD (polarization mode dispersion) value of optical fibers. The device is characterized by comprising a machine frame, an upper guiding rotation wheel, a rubbing twisting rotation wheel, a lower guiding rotation wheel, a linear guide rail, a sliding block, a jacking block, a connecting block for the rubbing twisting rotation wheel, a bearing, a cam, a tension spring, a tension-spring fixing block and a motor. The device disclosed by the invention has the advantages that the structure is simple, the reliability is high, the damages to optical fiber coatings are not easy to cause, and the influence on optical fiber strength is small.