Electrochemical properties of a series of ortho-phenylenediamines have been studied by using cyclic voltammetry and spectroelectrochemical method. The para-substituents, methyl and methoxy groups could provide the steric protection to the oxidized ortho-phenylenediamine, prevent it from undergoing dimerization and polymerization. Furthermore, strong electron donating methoxy group could stabilized the oxidized ortho-phenylenediamine, exhibits a more negative oxidation potential. UV/Vis/NIR spectroelectrochemical method was used to monitor ortho-phenylenediamine oxidation. Broad band absorptions at near-infrared region in the absorption spectra of compound 4、5 and 6 indicate intervalence charge transfer occurred between nitrogens.