A　monolithic　capillary　column　with　double　mixed-modes　of　hydrophilic　interaction/cation-exchange　and　RP/cation-exchange　stationary　phase　was　prepared　by　in　situ　thermal　polymerization　and　then　hydrolyzed　with　hydrochloric　acid.　The　polymerization　solution　containing　glycidyl　methacrylate　(GMA),　3-sulfopropyl　methacrylate　potassium　salt　(SPMA),　and　ethylene　dimethacrylate　(EDMA)　in　a　binary　porogenic　solvent　consisting　of　dimethylformamide　(DMF)　and　1,4-butanediol　was　polymerized　in　a　fused-silica　capillary　pretreated　with　3-(trimetoxysilyl)　propyl　methacrylate.　The　epoxy　groups　on　the　surface　were　hydrolyzed　to　diol　groups　with　hydrochloric　acid　to　enhance　the　polarity　of　the　stationary　phase.　By　simply　altering　the　ACN　content　in　the　mobile　phase,　two　mixed-mode　mechanisms　could　be　achieved　on　the　same　monolithic　column　in　different　mobile　phase　condition.　Hydrophilic　interaction　(or　hydrophilic　interaction/cation-exchange)　was　observed　at　high　ACN　content,　as　well　as　RP　(or　RP/cation-exchange)　was　observed　at　low　ACN　content.　The　monolithic　column　provided　good　selectivity　and　high　efficiency　for　separation　of　neutral　polar　analytes　and　basic　compounds.　Phenols,　anilines,　alkaloids,　nucleic　acid　bases,　and　narcotic　pharmaceuticals　have　been　successfully　separated.　Effects　of　salt　concentration　and　ACN　content　on　the　separation　have　also　been　investigated.　High　column　efficiencies　of　up　to　352　000　plates/meter　were　obtained　by　the　separation　of　narcotic　pharmaceuticals.