ABSTRACT Objective The purpose of this study was to evaluate the structural and functional changes of the mitral valve in patients with rheumatic heart disease and severe mitral stenosis (RMS) using the four-dimensional ultrasound automated mitral valve quantification technique (4DAutoMVQ). Method In this study, 57 RMS patients were prospectively selected as the case group, and 30 healthy subjects were simultaneously selected as the control group. Transthoracic echocardiography was used to acquire 2D and 3D images of the heart.The mitral orifice area was measured by two-dimensional tracing of the mitral valve orifice (MVA2D), Doppler pressure drop halving time method (MVAPHT), and mitral valve orifice three-dimensional tracing method (MVA3D). The mitral annular parameters were obtained by 4DAutoMVQ technology, including A-P diameter (AP), PM-AL diameter (ALPM), Inter-Trigonal Distance (ITD), Commissural Diameter (CD), Sphericity Index (SPI), Annulus perimeter (CA3D),Annulus Area 2D (AA2D), Annulus Area 3D (AA3D), Non-Planar Angle (θNPA) and Annulus Height (HA). At the same time, mitral valve leaflet parameters were collected, such as Tenting Height (Htent), Tenting volume (Vtent), Tenting Area (Atent), Anterior Leaflet Area (Aant), Posterior Leaflet Length (Apost), Anterior Leaflet Length (Lant), Posterior Leaflet Length (Lpost), Posterior Leaflet Angle (θpost) and Anterior Leaflet Angle (θant). In addition, mitral motion and deformation parameters are included, such as the Mitral Annular Excursion (DAmax), Mitral Annular Max Velocity (VADmax), and the Annulus Area 2D Fraction (AAF). Other parameters relate to the Mitral-Aortic Angle (θ). The differences in three-dimensional parameters between the case and control groups were compared, and correlation analysis was performed to confirm the relationship between MVA3D and CA3D, AA2D, and AA3D valve ring parameters. At the same time, the differences between MVA3D, MVA2D, and MVAPHT were statistically analyzed. Results The results showed that the AP, ALPM, ITD, CD, SPI, CA3D, AA2D, AA3D, θ NPA, Htent, Vtent, Atent, Aant, Apost, Lant, Lpost, θ ant ° and θ in the case group were significantly higher than those in the normal control group. In contrast, DAmax, VADmax, AAF, HA, and θ post were significantly lower than those in the normal control group, with statistical significance (P<0.05). There was no statistically significant difference (P>0.05) between the MVA3D, MVA2D, and MVAPHT in the case group. Correlation analysis showed no correlation between CA3D, AA2D, AA3D annulus parameters and MVA3D in RMS patients (r=-0.035， -0.100， -0.024, P>0.05). Conclusion 4DAutoMVQ technology can effectively provide information about the structure and function of the mitral valve in RMS patients: 1. The measurement results of 2D ultrasound and 3D ultrasound for MVA are consistent well. 2. Although the mitral valve orifice area of RMS patients decreased, the annulus was significantly expanded, and the displacement and deformation function of the mitral annulus also decreased.