The present invention relates an antifouling electrocatalytic composite membrane and a membrane reactor. The electrocatalytic composite membrane (3) consists of a substrate and a catalytic coating, wherein the substrate is selected from a conductive substrate or a nonconductive substrate coated with a conductive coating, and the substrate is a porous support having supporting, conducting and separating functions. The catalytic coating is supported or coated on the surface and in the pores of the conductive substrate or the conductive coating so as to increase the electrocatalytic activity of the substrate. The membrane reactor provides a trans-membrane pressure as the membrane separation power generated by a pump (7) and dead-end filtration or cross-flow filtration is applied, then the feed liquid permeates through the membrane from one side to the other to achieve the separation of the liquid; meanwhile, an electrocatalytic composite membrane (3) as anode and an auxiliary electrode (4) as cathode are connected to a power supply (1) separately by conducting wires (2) so that an electrolysis apparatus is formed. The electrocatalytic composite membrane (3) has a self-cleaning function and achieves the pollution-free operation during the membrane separation.