A voltage reference circuit providing a mean voltage of 281mV is proposed in this work. All transistors are biased in weak inversion region, and the 0.18um mix signal process is used in the simulation. This design is based on the weighted different threshold voltage between two devices, which has ultra low-power consumption of 1.5nW on 1V at room temperature. Besides, the temperature coefficient of voltage is as low as 16 ppm/°C at best@1V and 40 ppm/°C on average in a range from 0°C to 150 °C. The supply voltage of the proposed voltage circuit is from 0.65 to 5 V, and the power supply rejection ratio (PSRR) is −54dB@100Hz. The active area of circuit is 0.0013 mm2.