A low-voltage bandgap reference implemented in 0.18 mu m CMOS process is designed. The bandgap reference circuit is optimized by adjusting the ratio of the resistors, and reducing the working voltage of operational amplifier. It achieves the performance of a temperature coefficient of 25 ppm/degrees C in the range of 0 similar to 100 degrees C which works under the voltage of 0.8V. The simulated power supply rejection ratio is 46.3dB @1Hz and the line regulation is 1.5mV/V in the range from 0.8V to 1.8V.