An image processing system and a method for object-tracing are provided. The method includes: receiving a first wide field of view image and a first narrow field of view image, and determining a to-be-traced object therefrom and choosing one image therefrom for serving as a first output image; using an area size of the to-be-traced object in the first output image as a reference area; comparing the reference area with the area sizes of the to-be-traced object from a second wide field of view image and a second narrow field of view image respectively so as to determine one of that as a main image, and respectively zooming and deforming the main image and an area corresponding to the other image, and then fusing a zoomed and deformed second image as a second output image.