Two-dimensional (2D) membrane with ultrahigh permeability and precise sieving performance is highly desired. Herein, we have constructed a Janus composite membrane, which is integrated with carbon nanotubes (CNTs) and oxidized carbon spheres (OCS) modified with polyetherimide (PEI), through an interfacial self-assembly process. The designed Janus CNTs/OCS@PEI composite membrane has asymmetric micromorphology and wettability. The hydrophobic side is functioned as an active layer to inhibit concentration polarization during separation process. The superhydrophilic side can allow partial CNTs to stretch into its interior and form an interpenetrating network, which can weaken the Laplace pressure arising from the hydrophobic side. Hence, this membrane has the ability to reject various dye molecules, such as congo red (permeance flux of 3110.2 ± 285 L m? 2h? 1 bar? 1 and efficiency about 98.8%), which has transcended the majority of the separation membranes previously reported. Furthermore, this membrane can withstand physical damage and chemical corrosion that has presented stable rejection performance for dye molecules. This intriguing work would open the door to developing novel Janus materials to satisfy the water resources requirements of real-world applications.