The present invention provides a method for preparation of poly(o-phenylenediamine) nano-belt comprising mixing aqueous solutions of o-phenylenediamine and of oxidant in a mole ratio of 1:0.1 1 under stirring; standing for 0.5 2 hrs at room temperature; and obtaining poly(o-phenylenediamine) nano-belt. The method is suitable for large-scale production. In the absence of template and surfactant, aqueous solutions of o-phenylenediamine and of oxidant are mixed in a specified mole ratio and thus obtain a poly(o-phenylenediamine) nano-belt with length of several hundred micrometers, width of several hundred nanometers and thickness of tens nanometers. The method is simple, quick and suitable for large-scale manufacture. The poly(o-phenylenediamine) nano-belt thus prepared possesses excellent semiconductor properties and is one of the most promising conductive polymer materials.