The invention discloses an electrically enhanced internal anaerobic zero-valent iron reactor, belonging to the technical field of water treatment. Two graphite electrodes are arranged inside an anaerobic reactor and connected with an external direct current regulated power supply through a wire to simulate growth of microorganisms; meanwhile, the oxidation reduction process of the graphite electrodes also strengthens reductive decoloration of azo dyes. The graphite electrodes are arranged in the anaerobic internal biological zero-valent iron reactor, dissolution of iron is regulated by applying micro-voltage, and the buffer capacity of the reactor to acidification is strengthened. Coupling of an external power supply and zero-valent iron can also accelerate sludge granulation, efficiently enhance the decomposition capacity to organic compounds and realize rapid starting and high-efficiency running of the anaerobic reactor. A bench scale experiment shows that after the micro-voltage is applied, the rapid starting and the sludge granulation of the anaerobic reactor can be realized within 41 days, and the electrically enhanced internal anaerobic zero-valent iron reactor has stronger shock resistance.