Fe/C microelectrolysis process has low wastewater treatment efficiency and is prone to hardening problems, and is only suitable for treating acidic wastewater. In order to broaden the application range of Fe/C microelectrolysis process and improve the treatment efficiency, Fe/Mn/C ternary microelectrolysis system was constructed by adding zerovalent Mn and methyl orange (MO) simulated dye wastewater was treated. The morphology changes of iron, manganese and carbon and the compositions of surface elements were analyzed using SEM-EDS, Fourier transform infrared spectroscopy and Raman spectra. The changes of organic compounds in the wastewater were explored using UV-Vis spectra and three-dimensional fluorescence spectra before and after the reaction. Degradation performance of methyl orange was compared between Fe/Mn/C microelectrolysis and Fe/C microelectrolysis. Reaction mechanisms and reaction kinetics of methyl orange degradation were revealed using Fe/Mn/C ternary microelectrolysis system. The results showed that iron oxides, hydroxides and manganese oxides were existed on the surface of iron, manganese and carbon after the reaction. Fe/Mn/C ternary microelectrolysis broke nitrogen-nitrogen double bond of methyl orange and destroyed the structure of benzene ring. The degradation process of methyl orange conformed to second-order kinetics. After zero-valent Mn was added into Fe/C binary microelectrolysis system, the reaction efficiency constant of methyl orange degradation increased from 5.7381×10_^-4min_^?1 to 9.38336×10_^-4min_^?1. The degradation rate and degradation effect of methyl orange in the Fe/Mn/C microelectrolysis system was significantly better than those in the Fe/C microelectrolysis system.