0.6 μm SOI SONOS EEPROM transistors were fabricated with 0.6 μm SOI SONOS process, and their current-voltage characteristics both programmed and erased were discussed. The threshold window voltage was 5.04 V before radiation. Then these EEPROM transistors were radiated with Co-60 γ-ray at various radiation levels. It was showed that the EEPROM still had a threshold window of 0.7 V when the total dose reached 500 Krad(Si), satisfying the requirement of the memory circuit. The mechanism of the threshold shift due to total dose radiation was analyzed.