Background: Mobility and flexibility of anterior mitral leaflet (AML) are considered to be the important factor for mitral valve (MV) repair in rheumatic population, we try to use the bending angle of AML to quantify its' mobility and flexibility and investigate whether it can predict the success of rheumatic MV repair or not. Methods: Total 54 patients underwent rheumatic MV surgeries with mild lesions of subvalvular apparatus from August, 2017 to November, 2017 at the author institution, we divided the patients into MV repair and MV replacement groups which included directly MV replacement and repair attempt but failed repairing transfer to replacement intraoperatively. Patients' MV structure was carefully evaluated on transthoracic echocardiography (TTE) and scored by the Wilkins score (WS) preoperatively. The bending angle of AML was measured during systole and diastole at different level before surgery. Results: The differences of patients' demographic characteristics between repair group and replacement group were not statistically significant (P value >0.05) and the differences among B-angle, T-angle, Bs-angle, C-angle of AML between repair group and replacement groups were not statistically significant (P value >0.05). Only BT-angle in repair group was significantly larger than that of replacement group (21.56 degrees +/- 3.84 degrees, 10.29 degrees +/- 6.02 degrees, respectively, P<0.001), therefore the BT-angle was tested as a predictor of reparability by observing the receiver operating characteristic (ROC) curve (ROC area: 0.944, standard error: 0.06, 95% CI: 0.826-1), BT-angle of AML on preoperative transthoracic echo of 15.5 degrees or more predicts feasibility of rheumatic MV repair with 100% sensitivity and 85.7% specificity in patients with mild lesions of subvalvular apparatus. Logistic regression for a single area of calcification (diameter <0.8 cm) at commissure were shown that: beta: 0.08, Exp (beta): 1.083, P: 0.777>0.05, the minor single calcified area at commissure had no effect on reparability of rheumatic MV disease. The differences of total WS and each component score between repair group and replacement group were not statistically significant (P value >0.05). By observing the ROC curve for total WS (ROC area: 0.508), the WS cannot be a predictor for the rheumatic MV repair. Conclusions: The bending angle of AML which was considered as quantification of mobility and flexibility of AML can be a predictor for MV repair in patients with rheumatic heart disease (RHD). The small single area of commissural calcification had no effect on reparability of rheumatic MV disease. WS cannot appropriately predict the outcome of rheumatic MV repair.