In this work, an oil absorption material composed of self-crosslinking cellulose graft poly (butyl methacrylate) copolymers was prepared using the homogeneous atom transfer radical polymerisation process. Cellulose was dissolved in an ionic liquid ([Bmim]Cl) system and treated with neat trichloroacetyl chloride to produce macroinitiator (Cell-Cl3Ac). Then, butyl methacrylate was polymerised onto the cellulose backbone in a homogeneous DMF solution in the presence of Cell-Cl3Ac. Characterisation determined through FTIR, NMR, SEM, TEM and TGA measurements indicated that a graft copolymer with a cellulose backbone and PBMA side chains in a self-crosslinking 3D interconnected structure can be used as an oil absorbent. Grafting polymerisation conditions were subsequently investigated in detail as well as the relationship between the butyl methacrylate conversion and oil absorption performance of the products. The results indicate that when the butyl methacrylate conversion was 23.2%, the oil absorption abilities of the Cell-g-PBMA for motor oil reached 52.9 g g−1.