Background: Transcatheter aortic valve implantation (TAVI) is an alternative method to treat patients with severe aortic valve disease. Accurate measurement of the aortic valve annulus and selection of the appropriate artificial valve are critical to the success of TAVI. Multilayer spiral computed tomography (MSCT) is recommended as the "gold standard" for assessing the aortic valve annulus before TAVI. However, MSCT scanning may not be possible for patients with iodine allergy, renal failure, or pregnancy. The purpose of this study is to evaluate the aortic valve annulus by three-dimensional transesophageal echocardiography (3D-TEE) and compare the results with MSCT, exploring the feasibility of 3D-TEE to guide the selection of artificial valve implantation in TAVI.Methods: We retrospectively analyzed 74 patients who successfully underwent TAVI in our hospital. Before the operation, 3D-TEE and MSCT were used to measure the maximum diameter, minimum diameter, areaderived diameter, and perimeter-derived diameter of the aortic valve annulus, and the results were analyzed for consistency. To predict the valve size based on 3D-TEE and the MSCT area-derived diameter, we compared the differences between the predicted valve size and the actual implanted valve size, and analyzed the differences between 3D-TEE and MSCT for guiding the selection of the prosthetic valve size.Results: There was no significant difference between 3D-TEE and MSCT in the measurement of the maximum diameter, minimum diameter, area, and perimeter of the aortic annulus and their derived diameter (P>0.05). The intraclass correlation coefficients for the maximum diameter, minimum diameter, area-derived diameter, and perimeter-derived diameter of the aortic annulus were 0.89, 0.83, 0.84, and 0.92, respectively.There was no statistical difference in the accuracy of both methods, 3D-TEE and MSCT, in predicting different prosthetic valve sizes for TAVI (P>0.05).Conclusions: 3D-TEE and MSCT have good agreement for measuring the values of various parameters of the aortic annulus. The accuracy of both methods was similar for predicting the aortic prosthetic valve size. 3D-TEE may provide guidance for selecting the prosthetic valve size for TAVI.