The present disclosure provides a method and a circuit for signal collection of an image sensor. The image sensor includes a plurality of pixels arranged in an array, and each of the plurality of pixels include a photodiode. The method for signal collection includes: performing signal collection row by row on the plurality of pixels in each signal collection period, wherein the signal collection period comprises at least one reset frame and at least one clear frame; applying a forward bias voltage to the photodiode of each of the plurality of pixels being collected in each reset frame; and applying a reverse bias voltage to the photodiode of each of the plurality of pixels being collected in each clear frame. The solution provided by the present disclosure can ensure a better clearing effect and eliminate the impact of ambient light on imaging, while shortening the signal collection period.