Edge-element method is a new kind of calculation method based on the mesh of finite elements. Compared with the traditional finite-element method（nodal elements）

it has advantages of less variables and computing time（and storage） without distribution of spurious modes. In this paper the edge-element formulae for 3-D electromagnetic problems based on tetrahedra and calculation results for inhomogeneously filled rectangular cavities are presented. New forrmulae are also presented to allow quantitative comparison between the global matrices that arise from the alternative edge and nodal elements. The origin of zero eigenvalues and prediction of their total number are discussed with newly proposed forrmulae. Therefore this new method has been theoretically enriched and developed by this paper.