Reversed phase/ion exchange mixed-mode liquid chromatography plays a significant role in the separation of natural products, peptides and proteins.In this work, we designed a novel reversed-phase/anion exchange (RP/AEX) mixed-mode stationary phase named C 18SAX (Fig.1) based on polar-copolymerized approach.Chromatographic evaluations demonstrated that the C18SAX had 100% aqueous compatibility, typical reversed phase and ion exchange retention characteristics.The C18SAX was packed to SPE cartridge and applied for the pretreatment of aristolochic acids (AAs) extracted from Caulis Aristochiae Manshuriensis.The average recoveries of AA-Ⅰ and AA-Ⅱ were 72.36% and 105.59%, with RSD of 5.77% and 1.13%, respectively (as shown in Fig.2).The results proved that the aristolochic acids could be enriched by C 18SAX, and easily eluted in acidic conditions, indicating that C 18SAX has great potential in the enrichment of acidic compounds from complicated matrices.