An image registration method carried out by a computer, characterized by comprising: calculating a correlation coefficient image between a reference image and a floating image; calculating a gradient image of the correlation coefficient image; determining (S 160) a pixel with extreme correlation coefficient in the correlation coefficient image according to a pixel with extreme gradient in the gradient image; and registering (S 180) the reference image and the floating image according to the pixel with extreme value of correlation coefficient, wherein the correlation coefficient image is a digital matrix in which each pixel represents the correlation coefficient of the displacement between the reference image and the floating image corresponding to the pixel, characterized in that the determining a pixel with extreme correlation coefficient in the correlation coefficient image according to a pixel with extreme gradient in the gradient image comprises: searching for a pixel with a maximum value in the gradient image as the pixel with extreme gradient; determining a corresponding pixel in the correlation coefficient image according to a position of the pixel with extreme gradient; and finding the pixel with extreme correlation coefficient according to the corresponding pixel in the correlation coefficient image, wherein the finding the pixel with extreme correlation coefficient according to the corresponding pixel in the correlation coefficient image comprises: determining an adjacent pixel of the corresponding pixel in the correlation coefficient image as a search point; and traversing adjacent pixels of the search point and taking, if pixel values of the adjacent pixels are all smaller than a pixel value of the search point, the search point as the pixel with extreme correlation coefficient; otherwise, taking an adjacent pixel with maximum value as a new search point for re-finding. calculating a correlation coefficient image between a reference image and a floating image; calculating a gradient image of the correlation coefficient image; determining (S 160) a pixel with extreme correlation coefficient in the correlation coefficient image according to a pixel with extreme gradient in the gradient image; and registering (S 180) the reference image and the floating image according to the pixel with extreme value of correlation coefficient, wherein the correlation coefficient image is a digital matrix in which each pixel represents the correlation coefficient of the displacement between the reference image and the floating image corresponding to the pixel, characterized in that the determining a pixel with extreme correlation coefficient in the correlation coefficient image according to a pixel with extreme gradient in the gradient image comprises: searching for a pixel with a maximum value in the gradient image as the pixel with extreme gradient; determining a corresponding pixel in the correlation coefficient image according to a position of the pixel with extreme gradient; and finding the pixel with extreme correlation coefficient according to the corresponding pixel in the correlation coefficient image, wherein the finding the pixel with extreme correlation coefficient according to the corresponding pixel in the correlation coefficient image comprises: determining an adjacent pixel of the corresponding pixel in the correlation coefficient image as a search point; and traversing adjacent pixels of the search point and taking, if pixel values of the adjacent pixels are all smaller than a pixel value of the search point, the search point as the pixel with extreme correlation coefficient; otherwise, taking an adjacent pixel with maximum value as a new search point for re-finding. searching for a pixel with a maximum value in the gradient image as the pixel with extreme gradient; determining a corresponding pixel in the correlation coefficient image according to a position of the pixel with extreme gradient; and finding the pixel with extreme correlation coefficient according to the corresponding pixel in the correlation coefficient image, wherein the finding the pixel with extreme correlation coefficient according to the corresponding pixel in the correlation coefficient image comprises: determining an adjacent pixel of the corresponding pixel in the correlation coefficient image as a search point; and traversing adjacent pixels of the search point and taking, if pixel values of the adjacent pixels are all smaller than a pixel value of the search point, the search point as the pixel with extreme correlation coefficient; otherwise, taking an adjacent pixel with maximum value as a new search point for re-finding. determining an adjacent pixel of the corresponding pixel in the correlation coefficient image as a search point; and traversing adjacent pixels of the search point and taking, if pixel values of the adjacent pixels are all smaller than a pixel value of the search point, the search point as the pixel with extreme correlation coefficient; otherwise, taking an adjacent pixel with maximum value as a new search point for re-finding.