<p>A modified cellulose-based polymer absorbent was synthesized via suspension polymerization. Firstly, cellulose and glycidyl methacrylate (GMA) were combined in a catalytic transesterification reaction to form a cellulose precursor functionalized with methacrylate groups and unsaturated bonds. The structure of this precursor was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), Surface Energy Analysis, Carbon-13 Nuclear Magnetic Resonance (¹³C-NMR), and X-Ray Photoelectron Spectroscopy (XPS). The effects of the mass ratio of butyl methacrylate to styrene, as well as the amounts of initiator, cross-linker, porogen, dispersant, and cellulose precursor, on the oil absorption rate of the polymer absorbent were examined. Optimal synthesis conditions were identified, and the adsorbent's microstructure and adsorption mechanism were characterized by FT-IR, Scanning Electron Microscopy (SEM), Thermal gravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), and adsorption rate analysis. The adsorption kinetics model was also determined. Additionally, recyclability and oil–water separation tests were performed on samples prepared under optimal conditions. Results showed that the modified cellulose-based polymer absorbent has a stable structure with surface micropores, high absorption rates, fast adsorption kinetics, and excellent stability and oil–water separation capability, indicating potential applications in the removal of organic pollutants and organic solvents from water.</p>