Abstract: To address the challenge of balancing high dynamic range and high signal-to-noise ratio （SNR） in marine optical remote sensing, an on-board pixel-by-pixel adaptive imaging method based on a visible spectrum complementary metal-oxide-semiconductor （CMOS） detector was proposed. The implementation of this method involved a customized detector, an on-board processing algorithm, and ground calibration. The on-board processing software was developed using a high-performance field-programmable gate array （FPGA） platform, and a real-time decision logic for pixel-by-pixel and stage-by-stage gain was designed, enabling each pixel to dynamically select and output the highest gain that remained unsaturated. Through ground radiation calibration, the optimal linear operating ranges and switching gain thresholds for the four gain stages, including high, medium, low, and ultra-low, were precisely determined. On-orbit verification demonstrates that this method significantly improves the performance of the HY-3A medium resolution imaging spectrometer. Under the condition that the SNR satisfies the observation requirements, the maximum radiance is at least 8.9 times the typical radiance, by which the inherent conflict between high sensitivity and large dynamic range is effectively resolved, providing a reliable technical approach for high-precision ocean color remote sensing.