An image processing method and an image processing circuit are provided. The method and circuit are applied to motion estimation. The method includes the steps of: performing low-pass filtering on a first image and a second image, wherein the first image is part of a first frame, the second image is part of a second frame, and the first frame is different from the second frame; calculating a first characteristic value of the first image and calculating a second characteristic value of the second image; calculating a sum of absolute difference (SAD) between the first image and the second image; blending the difference between the first characteristic value and the second characteristic value and the SAD to generate a blended result; and estimating a motion vector between the first image and the second image according to the blended result.