The present invention discloses an image sensor, an image readout method, and an electronic device. The image sensor comprises: a pixel array and a plurality of readout conversion circuits, the readout conversion circuit comprises: a comparison circuit for comparing an output signal of the column pixel with a ramp signal to obtain a first output signal and a second output signal; a selection module for selecting the first output signal during a first sampling count, and selecting the second output signal during a second sampling count; a counter for counting according to the first output signal and the second output signal to obtain total quantization value of the first sampling count and the second sampling count, so as to obtain actual signal quantization result according to the total quantization value. The image readout speed of the image sensor is improved.