Wide Dynamic Range(WDR) readout circuits are crucial for high-performance photoelectric detection in complex scenes. Extreme conditions—such as coexisting strong backgrounds and weak targets or dramatic light fluctuations—are common in meteorological monitoring and deep-space exploration. Traditional circuits often struggle to balance sensitivity and saturation capacity. To meet the demands for high resolution and wide range，this paper presents a novel readout circuit with adaptive gain switching. This circuit is based on a Capacitive Transimpedance Amplifier(CTIA)and integrates a comparator and counter for adaptive integration control，alongside Correlated Double Sampling(CDS) and Pulse Width Modulation(PWM)digitization circuits. Designed and taped out in a 0. 5 μm 5 V-CMOS process，the results show an analog dynamic range of 97. 04 dB，a time-domain extension of 23. 52 dB，and a total dynamic range of 120. 56 dB.