Graphene oxide (GO) on a glassy carbon (GC) electrode was directly reduced at −1.0V in a phosphate buffer (pH 4.15) to form graphene/GC electrode, which was used for the electrocatalytic oxidative polymerizations of aniline, o-aminophenol, and m-aminophenol in the acidic solutions using cyclic voltammetry, amperometric and potentiometric methods. Cyclic voltammograms demonstrate that the oxidation peak of aniline on the first cycle shifts from 1.13V on the bare GC electrode to 0.76V on the graphene/GC electrode. In addition, both amperometric and potentiometric methods also demonstrate that graphene can effectively catalyze the electrochemical oxidative polymerization of aniline. Cyclic voltammetry confirmed that graphene can pronouncedly catalyze the electrochemical oxidative polymerizations of o-aminophenol and m-aminophenol, but graphene oxide hardly catalyzes the electrochemical oxidative polymerizations of aniline and its derivatives. The ESR spectrum of graphene is quite different from that of graphene oxide.