Abstract: The structure of the rectangular waveguide with transverse inductive diaphragms is approximately analyzed with the equivalent circuit theory of microwave transmission line two-port network. Calculation result shows that the widths of a pair of diaphragms can affect the phase and amplitude of the scattering parameter, but the diaphragm positions have no effect on the magnitude of the scatting parameter and the bandwidth. Microwave equivalent circuit transfer matrix of the rectangular waveguide with two pairs of symmetrical inductive diaphragms is studied with Matlab according to the counteracting of incidence and reflection, i.e. no reflection requirement. Longitudinal optimum spacing between two pairs of diaphragms is calculated on the basis of least insert attenuation. The bandwidth obtained with microwave equivalent circuit theory and the result of the high-frequency electromagnetic field software CST are nearly consistent, the difference between them is only 0.59%. The results have some significance for design of rectangular waveguide filters applied to high-frequency power vacuum device.