Abstract: This paper deals with the electromagnetic characterization of the transmission and scattering properties of a slit in a conducting plate for TM polarization. To alleviate computational constraints for the problem, a connection algorithm is developed based on microwave network theory.In this paper,the slit can be divided into sections and the generalized admittance matrix of each section can be computed by the boundary integral method. Using the connection algorithm,the aperture admittance matrix of the slit can be derived by cascading the admittance matrices of individual sections. Once the slit aperture admittance matrix is obtained,equivalent magnetic currents,the backscattered field, and the transmission coefficient are found by the generalized network principle.