One of the most important wave guiding structures in microwave
engineering is rectangular waveguides. In this paper full analysis of this waveguide is performed by a novel TLM (Transmission Line Method). In this method waveguide is meshed as network of very small transmission lines. Equations that rule this small line are known so by combining these small lines together a microwave network is combined. By using of microwave network theory, whole waveguide structure is analyzed. Also other shape of waveguide can be simulated by this method.