This study proposes a novel method to localize the mitral valve orifice in the three-dimensional left cardiac model reconstructed from Cardiac Magnetic Resonance (CMR) images. After acquiring both short axis and long axis CMR images, endocardium contours were delineated on all images while additional six points were marked to identify the mitral valve orifice on three long axis images. Contours from long axis images were registered to the short axis contours. The resulting registration parameters were stored. A three-dimensional surface model of the left cardiac structure was then reconstructed from the short axis contours. The six points representing mitral valve orifice in long axis images were projected onto the surface model using the registration parameters. A variational method was then applied to localize the mitral valve orifice on the surface model via minimizing the geodesic distance. Numerical examples show the robustness and effectiveness of the proposed method. Automatic location of mitral annulus orifice with the computational time per data set (22 frames) of five minutes would hold clinical potential as a real-time mitral valve assessment tool.