In order to achieve optical isolator,a system of one-dimensional magnetic photonic crystals with two metal films coated at its two sides was designed.The transmission properties of the structure through the modified transfer matrix method were studied.Due to the coupling of microcavity mode and the metal plasma,the structure shows one-way transmission feature and realizes the function of optical isolator.The performance of optical isolator is dependent on the incidence angle,thickness of the microcavity as well as the thickness of the metal.The isolator has good performance for an incidence angle of 45°,a microcavity thickness of 449 nm and a metal film thickness of 150 nm.The results are demonstrated through an electromagnetic field simulation based on the finite element solver.