Abstract: Infrared focal plane arrays (IRFPA) pose greater design and signal processing challenges than visible-light CMOS image sensors in space application, due to their intricate chip structures, specialized cooling packaging, and critical limitations of analog readout integrated circuits (ROIC) such as problematic data transmission and dark-field glow. This paper analyzes the defects of analog ROIC for space infrared detection, elaborates on the advantages of digital ROIC, and presents optimized on-chip analog-to-digital converter designs for space scenarios. The results demonstrate that on-chip signal processing based on digital ROIC can effectively increase frame rate, reduce system data processing burden and enhance imaging performance. This research provides valuable insights for the development of advanced space remote sensing and deep-space infrared imaging detectors.