To investigate 4H-SiC detector’s resistance to gamma irradiation, the detector was irradiated by 60Co gamma-ray(about 4×105 Ci), and the maximum cumulative dose was 1 MGy. The detector’s I-V characteristics and its performance in detecting charged particles were tested after gamma irradiation. The forward current increased and the reverse current decreased as the cumulative dose was increased. The ideal factor and Schottky barrier height were extracted from forward I-V curves, and the result showed that ideal factor increased and Schottky barrier height decreased after irradiation. The detector was exposed to 241Am source, and it was found that the detector’s performance degraded slightly after gamma irradiation. However, the detector behaved well in detection after it received gamma exposures at a dose of 1 MGy: its charge collection efficiency was 93.55% and its energy resolution was 2.32% in detecting alpha particles of 5.486 MeV. Therefore it has been proved that 4H-SiC detector has good resistance to gamma irradiation.