A CMOS bandgap reference circuit without resistors, which can successfully operate under 1V supply voltage is proposed. The improvement is realized by the technique of the voltage divider and a new current source. The most attractive merit is that the proposed circuit breaks the bottleneck of low supply voltage design caused by the constant bandgap voltage value (1.25V). Moreover, the temperature coefficient of the reference voltage V_ref is improved by compensating the temperature dependence caused by the current source. The simulation results using a standard CMOS 0.18 um process show that the value of V_ref can be achieved around 0.5 V with a minimum supply voltage of 0.85 V. Meanwhile, the temperature coefficient of the output voltage is only 3.5ppm/°C from 0 °C to 70 °C.