An adaptive CMOS detector that automatically adjusts gain based on light intensity was designed. The detector can automatically adjust the gain based on the intensity of light during integration, enabling adaptive sensitivity and dynamic range readouts in both low-light and high-light conditions. In this study, a new comparator circuit is introduced alongside the traditional CTIA circuit to control the size of the CTIA integration capacitor. By comparing the output voltage from short exposure with the reference threshold, the results are used to fine-tune the long exposure integration gain for each pixel. The design and simulation of a 128×1 linear array CMOS detector were conducted using 0.5μm 5V-CMOS technology. The simulation results demonstrate that the CMOS detector can adaptively adjust four different integration gains within a range of five orders of light intensity, covering photocurrents from 2pA to 100nA while maintaining excellent signal readout performance.