Piezoresistive pressure sensors with a twin-island structure were successfully fabricated using high quality Unibond-SOI (On Insulator) materials. Since the piezoresistors were structured by the single crystalline silicon overlayer of the SOI wafer and were totally isolated by the buried SiO₂, the sensors are radiation-hard. The sensitivity and the linearity of the pressure sensors keep their original values after being irradiated by ⁶⁰Go γ-rays up to 2.3×10⁴ Gy (H₂O). However, the offset voltage of the sensor has a slight drift, increasing with the radiation dose. The absolute walue of the offset voltage deviation depends on the pressure sensor itself. For comparison, corresponding polysilicon pressure sensors were fabricated using the similar process and irradiated at the same condition.