Abstract: Surface-polished IG110 nuclear graphite samples were irradiated with xenon ions. The surface morphology and irradiation damage was characterized before and after irradiation. Irradiation at room temperature induced severe anisotropic swelling of the graphite crystallites, but the swelling did not cause intergranular cracking, which was ascribed to the well-known irradiation-induced creep of unclear graphite. The severe swelling caused the shrinkage of many pores in the unclear graphite, indicating that irradiation to a certain dose would not enhance the salt infiltration into the unclear graphite in molten salt reactors. Raman spectra showed that G peak width increased monotonically with the increasing dose, and decreased gradually with the increasing of the annealing temperature, thus showed a potential to characterize the irradiation damage in the unclear graphite.