Oil spills on the seawater happened along the last decade needs to be addressed to prevent marine ecosystem destruction. The challenges encourage researchers to develop high-performance adsorbents. This study aims to investigate the adsorption capacity of magnetite-cellulose aerogel derived from Ramie stems in the oil-seawater mixture. The novelty of this research is the utilization of new and largely available ramie cellulose material combined with magnetite in simple alkali-urea method followed by coating using water repellant. Aerogel was synthesized by dissolving pulp of Ramie in NaOH-urea solution with urea addition of 3–6 g/g pulp and magnetite of 0–150 mg/g pulp. The mixtures were processed with sonication, coagulation, solvent exchange, freeze drying, and coating. The modified magnetite aerogel was analyzed for adsorption capacity, density, porosity, and measured contact angle. This research succeeded in synthesizing cellulose-magnetite aerogel from Ramie with density and porosity ranging from 0.11–0.22 gr/cm3 to 0.89–0.93, respectively. The characterization showed that the aerogels were arranged of macroporous structure and hydrophobic properties with a contact angle of 139°. The optimum adsorption capacity was 5.2 g diesel Dexlite/g aerogel and 7.2 g used lubricant oil/g aerogel at urea variations of 5 g/g pulp and magnetite 150 mg/g pulp. From this study, cellulose-magnetite aerogel from Ramie can be a solution to overcome the problem of oil spills with the advantages of being eco-friendly, abundant, and low cost.