Mixed matrix membranes (MMMs) are currently the focus of research due to their possible high separation performance in separating CO 2 process. However, inorganic nanomaterials are easy to agglomerate so as to affect CO 2 separation performance. In order to overcome the agglomeration of nanomaterials in MMMs, a new filler, Al 2 O 3 /PDA-TIL, was prepared, in which ionic liquid (TIL) was introduced on the surface of nano-Al 2 O 3 by TIL grafting polydopamine coated on aluminum oxide. And a new type of Al 2 O 3 /PDA-TIL/ Pebax MMMs membrane was prepared by the blend of new fillers and Pebax.The properties of MMMs prepared were characterized by SEM, FTIR, XRD, XPS, etc. Results showed that TIL had reacted with PDA to form Schiff base structure, indicating that TIL had been successfully grafted onto PDA coated on Al 2 O 3 . As a result, TIL on the surface Al 2 O 3 successfully reduced the agglomeration of Al successfully reduced the agglomeration of Al 2 O 3 in the membrane and improved the separation of CO 2 . The gas permeability test results showed that the CO 2 permeability of MMMs increased from 60.69 Barrer to 101.12 Barrer, and the CO 2 /N 2 selectivity increased from 49.34 to 79 at 30 C and 0.1 MPa. Therefore, Al 2 O 3 /PDA-TIL/Pebax membrane has a good application prospect in CO 2 separation process.