Disclosed are a CMOS image sensor having a wide dynamic range and a sensing method thereof. Each unit pixel of the CMOS image sensor of the present invention includes multiple processing units, so that one shuttering section for the image generation of one image frame can be divided into multiple sections to separately shutter and sample the divided sections by each processing unit. Thus, the image sensor of the present invention enables many shuttering actions to be performed in the multiple processing units, respectively, and the multiple processing units to separately sample each floating diffusion voltage caused by the shuttering actions, thereby realizing a wide dynamic range.