1. An image processing method for object-tracing, comprising: (a) receiving a first wide field of view image and a first narrow field of view image, and determining a to-be-traced object therefrom; (b) choosing a first output image from the first wide field of view image and the first narrow field of view image, and using an area size of the to-be-traced object in the first output image as a reference area; (c) receiving a second wide field of view image and a second narrow field of view image, and comparing the reference area with a wide field of view area size of the to-be-traced object in the second wide field of view image and a narrow field of view area size of the to-be-traced object in the second narrow field of view image respectively; (d) when the wide field of view area size is closer to the reference area, zooming and deforming the second wide field of view image according to a ratio of the wide field of view area size to the reference area, as well as zooming and deforming a corresponding area in the second narrow field of view image with respect to the wide field of view area size; (e) when the narrow field of view area size is closer to the reference area, zooming and deforming the second narrow field of view image according to a ratio of the narrow field of view area size to the reference area, as well as zooming and deforming corresponding area in the second wide field of vie image with respect to the narrow field of view area size; and (f) fusing the zoomed and deformed second wide field of view image and the corresponding area in the narrow field of view, or the zoomed and deformed second narrow field of view image and the corresponding area in the wide field of view to generate a second output image.