During left-sided cardiac valve surgery in patients with mild or no tricuspid regurgitation (TR), the tricuspid valve exploration plays a vital role in the decision-making of concomitant tricuspid annuloplasty. Currently lack of an appropriate standard to define tricuspid annular dilatation is a challenge. The aim of this study is to introduce and evaluate an alternative intraoperative method for Tricuspid Valve annuloplasty based on annular circumference that could trace the extent of annular dilatation and predict TR-progression, which can also guide the surgeons to intraoperative decision.From January 2011 to December 2011, 131 patients (73 females, 58 males, and mean age 54±10.8) were selected for the study underwent left-sided cardiac valve surgery at Anzhen Hospital, all the subjects preoperatively diagnosed with non-significant TR. The enrolled subjects were followed-up over 5years for TR-progression. Tricuspid annular circumference (TAC) measurement was performed via special sizer for each patient, and the obtained values divided on the subject's body surface area (BSA) to achieve the tricuspid annular circumference index (TACI). The endpoint was set as the TR-progression by more than two grades, or a final TR grade ≥3+.The mean follow up period was 68±3.8 months (range, 60-77 months). In univariate, multivariate and logistic regression analysis three variables were noticed to be associated with TR progression, female gender (P<0.002), body mass index (BMI) (P<0.021), and intraoperatively measured TACI (P<0.001). But in multiple regression the TACI (OR 0.812; 95% CI: 0.748-0.883; P<0.001) was the single parameter which significantly related to TR-progression. Based on the receiver-operator curve (ROC), it was likely to derive an optimal cut-off 80.2 mm/m2 which could predict the postoperative development of TR with acceptable sensitivity and specificity 69%, 89%.Patients with mild or no TR undergoing left-sided valve surgery, intraoperative measurement of the TAC proved to be an ideal method to judge the tricuspid-annulus, it is capable to predict TR-progression. For prophylactic tricuspid repair a presumed TACI of 80.2 mm/m2 is recommended as an indicative threshold.