The dispersion degree of polarization, a new definition of the depolarization degree of partially polarized beams, is first proposed, to the best of our knowledge, to measure the performance of fiber depolarizers. First, the description of the polarization based on the Poincaré sphere is introduced. Then, the modified Delaunay triangulation algorithm is introduced, and the calculation formula of the dispersion degree of polarization is given based on this algorithm. The experimental device was set up, and the dispersion degree of polarization of the depolarized light after the fiber depolarizer was measured to be 47.3%. The components and proportions of polarization in the depolarized light were also obtained. Compared with the degree of polarization, the dispersion degree of polarization can quantitatively analyze the light polarization evaluation in the time dimension and provide a numerical reference for improving the depolarizer, thus increasing the fiber sensor's accuracy.