Pixel-level analog-to-digital converters are widely used in infrared, visible and terahertz imaging and other fields due to their unique integrated position with high frame rate, large dynamic range, low power consumption and low noise. In this paper, the principle of mainstream pixel-level analog-to-digital converter structure was introduced; the research progress of pixel-level analog-to-digital converter in dynamic range, power consumption, area and noise and other performance parameters were analyzed; finally several key technologies in each improvement direction and makes prospects were compared and summarized.