Amorphization and nanohardness changes of SiC irradiated with 7 MeV Xenon ions at doses from 0.006 to 2 dpa were investigated. At a dose of 0.6 dpa, the results of Raman spectrum reveal the formation of Si–Si and C–C bonds within the SiC network while TEM results show the appearance of amorphous islands. The hardness of irradiated SiC is regarded as a combined result of covalent-bond damage and hardening effect of defects. In the low dpa regime (<0.06 dpa), the hardness of irradiated SiC increases with increasing dose, which is mainly caused by hardening effect. Up to 0.06 dpa, the hardening increases about 20.3%. And an equilibrium is reached between the covalent-bond damage and the hardening effect when irradiated SiC begins to amorphize (0.6 dpa). Above the dose of 0.6 dpa, the hardness decreases strongly due to the grievous covalent-bond damage.