Elastic optical network (EON) has been receiving extensive attention due to its inherent flexibility and the efficiency with which it allocates fiber bandwidth. Depending on the physical impairment, the distance adaptive modulation scheme can be adopted to ensure the transmission quality. However, distance adaptive modulation scheme will occupy more spectrum resources for the long-distance path. A segmentation modulation based spectral allocation scheme for EON is proposed to shorten the distance of each section by making working path segmentation, which reduces the occupied frequency slots (FS) by adopting high-level modulation. As a result, the proposed scheme will efficiently reduce the allocated FS and improve the overall spectrum resource utilization of the network.