The invention discloses a subwavelength plasmon polarization converter which comprises an incident polarizer and an emission polarizer which are separated by a medium or air layer. Both the incident polarizer and the emission polarizer are made of plasmon materials, small holes with subwavelength dimensions are engraved on the two polarizers, an included angle is formed between each small hole on the incident polarizer and the corresponding small hole on the emission polarizer, and the end points of the above two small holes are in intersection. When the included angle of two small holes is less than 90 degrees, the incident polarizer only allows the coupling entering of one polarized electromagnetic wave, and the emission polarizer only allows the emission of an electromagnetic wave which is orthogonal with the above polarized direction. By using a near field coupling effect between orthogonal rectangular holes, according to the system, the limitation of the Malus law can be broken, and thus the electromagnetic wave generates effective transmission and the polarization direction is rotated for 90 degrees. The converter can be used as a single-direction transmitter, a subwavelength switch and a modulator.