Objective To observe the value of mitral annular calcification （MAC） score based on cardiac plain CT for predicting intraoperative surgical procedure change of mitral regurgitation （MR）. Methods Totally 182 MR patients were retrospectively enrolled and divided into MAC group （n=57） and non MAC group （n=125） based on the presence or not of MAC, and clinical and imaging data were compared between groups. Logistic regression analysis was used to observe the impact factors of surgical procedure change. The receiver operating characteristic curve was drawn, the area under the curve （AUC） was calculated to explore the efficacy of MAC score for predicting surgical procedure change. Results Significant differences of the proportions of hypertension, atrial fibrillation （AF）, mitral valve repair, mitral valve replacement, aortic valve replacement, tricuspid valve repair and surgical procedure change, as well as of admission left atrial diameter （LAD）, admission left ventricular end-diastolic volume （LVEDV）, admission left ventricular ejection fraction （LVEF）, aortic valve stenosis, aortic regurgitation, the proportion of mitral stenosis （MS） and follow-up LAD were found between MAC group and non MAC group （all P＜0.05）. Then the patients were divided into surgical procedure change group （n=50） and non-change group （n=132）, and significant differences of patients’ gender, AF, MAC, MAC score, admission LAD, aortic valve stenosis, MS and MR degree were found between surgical procedure change group and non-change group （all P＜0.05）. MAC score was an independent impact factor of intraoperative surgical procedure change of MR （P＜0.001）, with AUC of 0.757. Conclusion MAC score based on cardiac plain CT could be used to predict intraoperative surgical procedure change of MR.