In this paper a modified self-organized algorithm for the generation of tetrahedral meshes is introduced for the optimization of meshes in the FEA. First

a geometric method is applied to reconstruct a classified volume data of specified size from the triangular surface model in this method and a balanced octree based on the given surface model is built to compute a 3D array

which used to control the mesh size. Then

the volume data is converted into a boundary indicator array in which different iso-surfaces are conformed in the neighborhood. Tetrahedral meshes can be generated finally by combining our improved self-organized algorithm with the interpolation function of the related 3D data. The experimental result shows that this method can be used to generate high quality tetrahedral meshes at higher proportions and enhance the ability to reduce the number of slivers. It also ensures the conformation of the boundary additionally. The algorithm in this paper can provide an effective and robust method when building finite element models for watertight 3D surface meshes.