Abstract: The aim of present study was to determine the effects of diameters of sinotubular junction and maximum sinus on aortic valve closure function. The 3-dimensional geometry of a base aortic valve was reconstructed using the geometric constraints and modeling dimensions suggested by Labrosse,and then the diameters of sinotubular junction and maximum sinus were modified to create six geometric models with different dimensions. The models were simulated in a controlled situation which focused on the closing diastolic phase of the valve,starting with an almost closed valve. The pressure was raped from 0up to 10. 665 kPa. The performance of the aortic root was quantified in terms of value and position of maximum stress,annulus diameter as well as normalized ratio of cusp coaptation area.Resultsshow that the maximum stress values occur at the connection between valve leaflets and sinuses for all models.Annulus diameter was increased 8. 3% with sinotubular junction diameter increased 1. 2 times. Relative changes of normalized cusp coaptation area were less than 5% for all six models. Compared with the maximum sinus diameter,sinotubular junction diameter has far more influence on annulus diameter,namely,on the function of aortic valve,because increasing the annulus diameter decreases the leaflet effective coaptation for the same aortic root.