Objective To evaluate a score system to allow stratification of complexity in degenerative mitral valve repair. Methods We retrospectively reviewed the clinical data of 312 consecutive patients who underwent surgery for mitral valve repair and whose preoperative echocardiography was referable in our hospital from January 2012 to December 2013. A scoring system for surgical complexity was used based mainly on the preoperative echocardiography findings. Complexity of mitral valve repair was scored as 1 to 9, and patients were categorized into 3 groups based on the score for surgical complexity: a simple group (1 point), an intermediate group (2-4 points) and a complex group (≥5 points). There were 86 males and 35 females in the simple group (n=121) with an average age of 51.6±12.6 years, 105 males and 53 females in the intermediate group (n=158) with an average age of 51.1±12.8 years and 25 males and 8 females in the complex group (n=33) with an average age of 49.3±13.0 years. Results There was significant difference in surgical complexity in different groups. In the simple, intermediate and complex groups, the mean cardiopulmonary bypass time was 111.7±45.5 min, 117.7±40.4 min and 153.4±74.2 min (P<0.001), the mean cross-clamping time was 77.5±33.8 min, 83.2±29.9 min and 108.8±56.2 min (P<0.001), and the mean number of repair techniques utilized was 2.1±0.4, 2.4±0.6 and 2.8±0.8 (P<0.001). However, there was no significant difference in the early and late outcomes in different groups. Conclusion It is feasible to use echocardiography to quantitatively evaluate the difficulty of mitral valvuloplasty.