Computational image sensors with CNN processing capabilities are emerging to alleviate the energy-intensive and time-consuming data movement between sensors and external processors. However, deploying CNN models onto these computational image sensors faces challenges from the limited on-chip memory resources and insufficient image processing throughput. This work proposes a 3D-stacked NAND flash-based computing-in-memory under image sensor architecture (CIMUS) to facilitate the complete deployment of CNN model. To fully leverage the potential of high bandwidth from the 3D-stacked integration, we design a novel distributed CNN mapping and dataflow to process the full focal plane image in parallel, which senses and recognizes ImageNet tasks with >1000fps. To tackle the computational error of inputs “0” in 3D NAND flash-based CIM, we propose an input-independent offset compensation method, which reduces the average vector-matrix multiplication (VMM) error by 48%. Evaluation results indicate that CIMUS architecture achieves a 9.8× improvement in CNN inference speed and a 33× boost in energy efficiency compared to the state-of-the-art computational image sensor in the ImageNet recognition task.