To preprocess mammograms for computer-aided diagnosis, this paper mainly researches the extraction of calcification region in mammograms. After the background segmentation to mammogram, it firstly makes the pick-up of the mammary region by using the improved area extension, and then uses the method of improved unsharp masking for image enhancement in the pick-up of the mammary region. It highlights the region of calcification points, and picks up the region of interest (ROI) which may contain calcification based on the characteristics of calcification and a suitable threshold. The result shows that this method can complete the extraction of calcification region of interest, helping to improve the accuracy of diagnosis of mammary diseases.