A dual-camera synchronous exposure method is applied to electronic equipment comprising a first camera and a second camera. The method comprises the following steps: acquiring brightness information from a preview image collected by the first camera, calculating the saturation of the preview image, and calculating the quality of the preview image according to the saturation; updating the brightness information in the preview image according to the way of increasing the default step size, calculating the saturation of the preview image, and calculating the quality of the preview image according to the saturation until judging that the quality of the preview image declines; and when the quality of the preview image declines, calculating the exposure value of the second camera according to corresponding brightness information, and when detecting a shooting instruction of a user, making the first camera and the second camera carry out exposure shooting according to the exposure value. The invention further provides a dual-camera synchronous exposure system. The quality of composite images can be improved.