Abstract: To address the issue of insufficient open-loop gain stability in operational amplifiers (op-amps) over a wide temperature range (−40 ℃ to 225 ℃), this paper proposes a high-gain-stability rail-to-rail operational amplifier design method based on Reverse Body Biasing (RBB) technology. Fabricated in a 180 nm Partially Depleted Silicon-on-Insulator (PD-SOI) process, the proposed design introduces RBB at the output stage of the op-amp to enhance the output resistance and thus the open-loop gain. A dedicated charge pump is designed to generate the RBB voltage, while over-voltage protection circuits and a low-dropout regulator are integrated to suppress the over-voltage issues and output voltage fluctuations induced by RBB. Simulation results demonstrate that over the full temperature range of −40 ℃ to 225 ℃, the RBB-enhanced op-amp achieves an open-loop gain of 115.5 dB, representing an improvement of 19.3 dB over the conventional structure. Furthermore, the gain fluctuation across the entire temperature range is only 2.0 dB, corresponding to a 75.6% reduction compared with the conventional design.