Objective To observe whether the adoptation of tricuspid annulus diameter as surgical indication for tricuspid annuloplasty will reduce the occurrence of moderate-severe tricuspid regurgitation(TR) in patients after mitral valve replacement (MVR). Methods Between April 2005 and June 2006, MVR was performed in 56 patients with no or mild TR in our Department. The patients were divided into two groups according to tricuspid annulus diameter(TAD)/body surface area (BSA)≥21mm/m2. Tricuspid annuloplasty group(TA group): 22 cases, male 8, female 14, age 45.0±7.7 years, TAD 36.8±3.8mm, BSA 1.57±0.15m2, New York Heart Association(NYHA) functional class Ⅲ/Ⅲ-Ⅳ 18/4, sinus rhythm(SR)/atrial fibrillation (AF) 2/20. Notricuspid annuloplasty group (NTA group): 34 cases, male 9, female 25, age 42.9±11.0 years, TAD 28.5±4.4mm, BSA 1.58±0.13m2, NYHA Ⅲ/Ⅲ-Ⅳ 28/6, SR/AF 9/25. Kay annuloplasty was performed for TA group patients. The patients were followed in outpatient clinical regularly and evaluated by echocardiography at 6 months after operation. Results All patients recovered and were discharged from hospital. The duration of follow-up was 11.0±2.4 months. Except 2 cases, all patients received echocardiography evaluation at 6 months after operation. There were no significantly differences between two groups patients in general clinical characteristics (Pgt;0.05). Compared with NTA group before operation, right atrial diameter (RAD, 49.3±7.0mm) and TAD(36.8±3.8mm) were bigger and more mild TR in TA group (Plt;0.05). RAD(44.1±8.9mm) and TAD(28.9±6.1mm) reduced and the proportion of TR degree improved (Plt;0.05) in TA group but did not occur in NTA group after surgery (Pgt;0.05). There were three cases of moderate TR in NTA group. Conclusion Tricuspid annuloplasty adopting TAD as surgical indication may reduce the occurrences of postoperative moderate-severe TR for patients of MVR with no or mild preoperative TR.