Porous poly(glycidylmethacrylate-co-divinylbenzene) (PGMA-co-DVB) microspheres with an average size of 4.6 μm were prepared using a multistage emulsion polymerization method successfully and were subsequently modified by diazoresin (DR). Three kinds of porogens (toluene, cyclohexanol and dodecanol) were applied and porous microspheres with different morphologies were obtained. Porous PGMA–DVB microspheres resulting from toluene were selected for further modification with DR due to their large specific surface area and good pore structure. These microspheres were modified through the hydrolysis of epoxy groups and a photocuring reaction with DR. After treatment with UV light, the hydrogen bonding between hydrolyzed microspheres and DR was converted into covalent bonding through a unique photochemistry reaction of DR. Porous PGMA–DVB–DR microspheres were used as the stationary phase for high performance liquid chromatography (HPLC). Depending on the chemical structure of DR, the DR modified PGMA–DVB stationary phase can be used to perform mix-mode separation mechanisms, including reversed phase (RP) and hydrophilic interactions. Therefore, baseline separation of benzene analogs was achieved by using the porous PGMA–DVB–DR particles as packing materials, and the by-product of hydrophilic acetic acid was rapidly separated from the N-vinyl-1,2,4-triazole product within 5 minutes. In addition, the DR-modified particles may be expected to be an alternative tool for organic acid separation due to the presence of secondary amino groups.