In this work, the mechanical propertied of calcification in diseased coronary artery was evaluated with atomic force microscope (AFM). The heavily calcified coronary artery was harvest from a cadaver’s heart. The artery slices with thickness of 10 um were prepared with cryosectioning. Staining with Alizarin Red has been performed to highlight the calcification region. Results have shown that the calcified areas have a significant larger stiffness compared with the surrounding plaque and the media layer of a healthy artery. The calcification showed a heterogeneous property with larger deviation in stiffness distribution. The staining process affected the mechanical properties. Results will enhance the mechanical property database in the literature.