Objective：To investigate the value of three-dimensional transesophageal echocardiography（3D-TEE） in the diagnosis of functional mitral regurgitation（FMR），and to explore the clinical safety and efficacy of mitral valve repair. Methods：Fifty cases of aortic stenosis（AS） or aortic regurgitation（AR） underwent aortic valve replacement（AVR），with or without FMR. All patients were treated with two-dimensional echocardiography and three-dimensional transesophageal echocardiography（3D-TEE）. For patients with moder－ate to severe FMR，mitral valve repair was performed on the ba－sis of aortic valve replacement. Echocardiographic parameters，perioperative death，aortic clamping time，intensive care unit（ICU） stay，and postoperative regurgitation correction were com－pared. Results：There were 24 cases of mitral valve repair and 26 cases without repair. There was no significant difference in base－line data between the 2 groups. The more serious MR，the larger mitral annular area（P=0.009），the smaller coaptation height（P=0.008） were found in MV repair group than in non repair group. There was a good consistency of mitral valve coaptation height between direct surgery and 3D-TEE measurement. There was no significant difference in aortic clamping time and postoperative ICU stay days（P=0.381，P=0.175）. In mitral valve repair group，1 cases died during perioperative period，and 1 cases died in the non repair group. There was no significant difference between the 2 groups（P=0.891）. Half a year follow-up of regurgitation corrective effect，there were 2 cases of mild mitral regurgitation，no case of mitral stenosis and regurgitaion aggravated in mitral valve repair group. There were 1 case of deteriorational mitral regurgitation and 1 case of mild mitral regurgitation in non-MV repair group. In addition，in mitral valve repair patients，the area of FMR mitral annulus caused by AS was smaller than that of AR patients（P=0.028），and the coaptation height of mitral valve was higher than that of AR（P=0.017）. Conclusion：Mitral valve repair is safe and feasible in aortic valve replacement. 3D-TEE is of great value in evaluating the mechanism of FMR. FMR is often accompanied by annular dilation and mitral valve closure disorder. The pathological mechanism of AS and AR concurrent FMR may be different. It is suggested that when AS is concurrent with FMR，MV annular diameter and coaptation height are the criteria of MV repair.