Performance of the matching method which directly using SIFT feature points needs to be improved. This paper proposed an improved SIFT matching method which firstly uses the scale ratio histogram of the matched feature points to estimate the approximate scale ratio k of the image pair, then increases the base scale up to k times and extracts featur points points again for the higher resolution image, finally performs feature matching again to obtain the result. The experiment results show that, compared with the existing improved SIFT matching methods with scale difference, performance is improved significantly for structured image pairs.