A computer aided reconstruction and motion analysis method of mitral annulus is presented in this paper. To begin with, the boundary points on mitral annulus are marked by doctors interactively. Since these points are not distributed uniformly and sequentially, secondly, it is necessary to re-arrange these points into a set of series points on a contour, the saddle-shaped mitral annulus. Thirdly, in order to analyze 3D mitral annulus motion, the mitral annulus is modeled by 3D non-uniform rational B-spline (NURBS). Fourthly, the dynamic parameters of the mitral annulus throughout the cardiac cycle are computed in a 3D Cartesian coordinate system. The experiments prove that the dynamic mitral annulus reconstruction and analysis program using computer aided method is provided a possible and convenient tool to diagnose and analyze the malfunction of mitral annulus.