A low temperature bleach bandgap reference source with segmental curvature compensation is designed to solve the problem of poor first-order bandgap reference temperature coefficient. The conventional first-order bandgap reference is compensated by segmental curvature, and two types of exponential compensation currents varying with temperature are generated using a MOS tube operating in the subthreshold region. The first-order coefficient temperature curve is compensated at both high and low temperatures, and the temperature coefficient of the bandgap reference source is reduced. The results of a SMIC 0.18 μm CMOS process simulation show that the bandgap reference output voltage is 1.075 V at a supply voltage of 3.3 V. The bandgap reference designed in this paper is compared with a first-order bandgap reference without curvature compensation. The temperature coefficient decreases from 9.85×10⁻⁶/℃ to 1.58×10⁻⁶/℃ in the temperature range of −40–125 ℃ at the TT corner, and the power supply rejection ratio is −46.4 dB at 100 Hz.