Abstract: Periodically distributed metallic rods were introduced into the inner and outer conductors of the coaxial transmission line to form a two dimensional metallic photonic crystal structure. The circuit model of the metallic photonic crystal loaded transmission line was built up and the frequency characteristic of the model was studied. It is found that, the structure has two characteristic frequencies; the first band gap starts from the zero frequency and ends at the first characteristic frequency, and the first pass-band starts from the first characteristic frequency and ends at the second. A finite metallic rod array structure was simulated by the commercial software CST Microwave Studio. Because of the finite dimension of photonic crystals in the propagation direction, there exists a pass-band characterized by multi-peaked variations. The electromagnetic property of each propagation peak was analyzed, and its dispersion characteristics were studied.