An image sensor including a plurality of pixels and a plurality of pixel sensing circuits is provided. The pixels are arranged in a pixel array. The pixels are configured to sense an image to obtain a plurality of reference pictures. The pixels include a plurality of pixel types. The pixel sensing circuits are respectively and electrically connected to the pixels. The pixel sensing circuits are configured to respectively receive a photo current generated by each of the pixels. The pixels have different characteristic curves based on the pixel types, and at least one of an electrode structure parameter and an electrode bias of each of the pixels is determined according to a correspondingly characteristic curve. In addition, an image sensing method is also provided.