1. An auto-focusing optimization method for a camera, comprising the following steps executed by the camera: shooting, in an auto-focusing manner, at least a first image and a second image at a same position and a same shooting angle after the camera is started; synthesizing the first and the second image; and displaying an image after synthesis processing; wherein the step of synthesizing the first and the second image comprises: acquiring corresponding portions from the first and the second image and dividing the corresponding portions into pixel blocks conforming to a one-to-one correspondence relationship; evaluating the pixel blocks conforming to the one-to-one correspondence relationship in the first and the second image to obtain the pixel blocks of high definition; wherein the step of evaluating the pixel blocks conforming to the one-to-one correspondence relationship in the first and the second image to obtain the pixel blocks of high definition comprises: acquiring a pixel density ρi of each of the pixel blocks conforming to the one-to-one correspondence relationship in the first and the second image.