Abstract: The surface morphology, compositions, diameters, SiC grains and phase characteristics of SiC fibers irradiated by 246.8 MeV Ar¹⁶⁺ ions at different fluences were studied by means of field emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). SEM results show that with the increase of the ion fluence, the diameter of SiC fiber first decreases and then increases. Moreover, at the highest fluence (2.7×10¹⁵ ions/cm²) irradiation, the surface roughness of SiC fiber increases evidently, and a brittle fracture occurred. Meanwhile, the carbon concentration on SiC fiber surface decreases and silicon concentration increases gradually with the ion fluences, accompanied by an adsorption of oxygen. TEM observations reveal that with an increase in ion fluences, the size of SiC grains first decreases and then increases, and some amorphization occurred. Furthermore, a transformation from the amorphization to the recrystallization was observed at the highest fluence irradiation.