Porous materials with carboxyl-modified multi-walled carbon nanotube (C-CNT) were prepared and applied to enrich oleuropein. Surface area, pore volume, and average pore diameter increased with increasing C-CNT content, and adsorption capacity was greatly enhanced. The results indicated that pseudo-second-order kinetics could describe the whole adsorption process, while intraparticle diffusion model fit the experimental data for the second stage (10–300 min). It suggested Freundlich isotherm model could describe the adsorption process. It showed that the porous materials exhibited excellent reusability and during six adsorption-desorption cycles, adsorption capacities showed no obvious loss. The high adsorption capacities, easy desorption, and remarkable reusability made the prepared porous materials as novel adsorbents for the enrichment of oleuropein. This study indicates porous materials with carboxyl group, large surface area, pore volume, and average pore diameter are favorable for oleuropein enrichment, providing an idea to design porous materials with carboxyl groups for oleuropein enrichment.