The eigen-properties of the cylindrical coaxial cavity have been investigated by FEM. The eigen-equation has been constructed basing on tangential edge vectors of the tetrahedral element. It was retreated with the shift-invert strategy to maintain the calculation stability. Krylov- Schur iteration method has been applied to it in order to obtain the eigen-pairs of TM and TE modes. Eigen-modes were calculated from the unitary similar transforming matrices of this iteration loop. Eigen-values have been determined from diagonal components of the Schur matrix. The eigen-pairs have been revealed as a result in the schematic representations for each modes. The eigen-modes were so complex that the surface features also have been shown in accompanying with them to identify their characteristics.