In this paper, the failure mode and mechanism of silicon carbide (SiC) Schottky barrier diode (SBD) irradiated by high-energy tantalum (Ta) ions are studied. The experimental results show that the reverse bias voltage during irradiation is the key factor causing the failure of SiC SBDs. When the reverse bias of the device is 400 V, the heavy ions will cause the single event burnout (SEB), and a “hole” formed by the melting of SiC material appears in the irradiated device. When the reverse bias is 250–300 V, the failure is manifested as the off state leakage current increases with the ion fluence. The higher the bias voltage of the device, the higher the leakage increase rate caused by heavy ions. For the devices with increased leakage, the leakage channels caused by heavy ions are found in the whole active region, based on microscopic analysis. The TCAD simulation results show that the incidence of heavy ions will lead the lattice temperature to increase in the device, and the maximum lattice temperature increases with bias voltage increasing. When the bias voltage is large enough, the local lattice temperature inside the device reaches the melting point of SiC material, resulting in SEB. When the bias voltage is relatively low, the lattice temperature is lower than the melting point of SiC material, so it will not cause burnout. However, the maximum lattice temperature in the device is concentrated near the Schottky junction, and the melting point of Schottky metal is much lower than that of SiC material. This may lead the Schottky junction to damage locally and eventually produce leakage path.