Abstract: Image scrambling transformation is a common method in information hiding and image encryption. How to evaluate the advantage and disadvantage of scrambling transformation is the hot and difficult issue of research. The method that position change based on scrambling in front and back can be the standard of the measurement. But the positional change can not stand for the change of the pixel value， and regarding an image as a whole may produce deviation. In order to overcome the shortcoming, it proposes a evaluation method of image scrambling degree, which is based on point-relativity. It measures the relative differences of a point and adjacent point in scrambling front and back. As the simulation result of Matlab, it shows that the method can measure the relationship between the times of image scrambling and scrambling degree, while it can be good consistency with human vision.