This study was conducted to access the catalytic performances and reaction mechanisms of Graphene Electroactive Membrane (GEM). The GEM was prepared by vacuum-pressing method, and characterized by FESEM and FTIR. Catalytic performances were measured in the index of decolorization ratio and mineralization rate. Active species were recognized by scavengers for investigating reaction mechanisms. The impacts of current intensity and water flux on catalytic performances were presented to illustrate the mechanisms of GEM electro-catalysis deeply. According to the results, the method of GEM preparation was reliable and Graphene was an appropriate material for Electroactive Membrane (EM). Compared with EM electro-catalysis and GEM with no electro-catalysis (GEM-NEC), the mineralization rate increased by 56.1% and 28.8% respectively, and the decolorization rate increased by 45.5% and 29.8% respectively. The decolorization rate of GEM electro-catalysis with 0.2 M Ammonium Oxalate (Scavenger of electron hole) decreased 32.7% more than GEM electro-catalysis with no scavenger. Thus, direct oxidation was the main mechanism of GEM electro-catalysis, which was very different from traditional electro-catalysis. When current intensity was less than 20 mA and water flux was higher than 3 mL/min, decolorization ratio increased dramatically. Thus, electro-catalytic process and adsorption-diffusion process played important roles in GEM electro-catalysis process. The GEM electro-catalysis was an effective and stable advanced wastewater treatment for removal of organic pollutants.