The synergetic effects of High Temperature Gate Bias (HTGB) (0 h, 162 h, 332 h) and Total Ionization Dose (TID) radiation (0 kGy, 1 kGy, 3 kGy, 5 kGy, 10 kGy) response of 1200 V commercial SiC power MOSFETs were studied, along with annealing characteristics at room temperature. Electrical parameters were investigated with Current-Voltage (I-V) and Capacitance-Voltage (C-V) measurements. Results show that Gate Threshold Voltage (Vth) is sensitive to combination of HTGB and TID. Gate Leakage Current (Igss) and Vth increase while Input Capacitance (Ciss) decrease after HTGB stress. Drain-Source Leakage Current (Idss) and Igss rise up due to TID radiation while Ciss and Vth decrease. HTGB mitigates the shift of parameters due to radiation to some extent, especially Idss. No obvious annealing effect was observed at room temperature for one week on all Device Under Tests (DUTs) in this work.