The electrochemical reduction characteristics of nitrobenzene were investigated using cyclic voltammetry. In addition, the difference in reduction mechanisms between Master Builders' iron and the catalyzed Fe-Cu process was discussed in this paper. The results showed that nitrobenzene was reduced directly on the surface of copper rather than by the hydrogen evolved at cathode in the catalyzed Fe-Cu process. The reduction was realized largely by the hydrogen evolved at cathode in Master Builders' iron. Both acidity and basicity favored the direct reduction at the copper electrode. The catalyzed Fe-Cu process was superior to Master Builders' iron in treating nitrobenzene-containing water, withal. This advantage was particular noticeable under alkaline conditions. The reduction was investigated in the cathode and anode compartments, respectively, and the experimental results showed that the direct pathway had a large role in the reduction by the catalyzed Fe-Cu process. To reduce nitrobenzene directly at the copper electrode is easier than to reduce it by the hydrogen evolved at cathode, copper could be regarded as the electrocatalyst in this case. The influence of copper usage on the treatment efficiency by the catalyzed Fe-Cu process was also studied. The results indicated copper increased the reduction rate. The catalyzed Fe-Cu process is of practical value.