A new type of photo-electro-chemical catalytic reactor was designed. The cathode of the reactor was made of highly pure graphite and the anode was made of titanium dioxide. A saturated calomel electrode (SCE) was so used as the reference electrode that the electric potential of the cathode was determined. Under the condition of ultraviolet radiation and anodic bias-voltage, reactive brilliant red X-3B was degraded in the reactor synchronously by the process of photoelectrocatalysis with titanium dioxide anode and electrogenerated hydrogen peroxide through reducing dissolved oxygen with graphite cathode. With the cooperation of the cathode and the anode, impressive decolorizing efficiency of reactive red X-3B has been achieved. The results showed that, when the concentration of reactive brilliant red X-3B was 25mg••L-1 and the inert supporting electrolyte concentration was 0.005 mol•L-1 (1000mg•L-1) sodium sulfate, initial solution ph=4, and cathodic potential -Ec = 0.60 V, under UV radiation as well as constantly pumping air into the reactor, decolorizing efficiency of 79% has been achieved.