Protecting the environment is important for its impact on the life of humans and organisms. Oil pollution is one of the most important factors affecting the life of creatures. Here we are looking for the way to magnetize oil contamination by modified sawdust. The iron oxide nanoparticles were coated in situ on the sawdust using co-precipitation method, which magnetized the sawdust. Subsequently, the magnetic sawdust was successfully functionalized with a saline coupling agent to form a highly hydrophobic and oleophilic surface. FE-SEM, FTIR, EDXA, VSM, WCA and optical microscopy were performed to complete characterization of the products. In addition, a new magnetorheological (MR) fluid based on the crude oil and magnetized sawdust was developed and its rheological properties studied by a rheometer furnished with a magnetic field generator. The results were completely fitted using Bingham model. The strong MR response induced in the crude oil by adding the modified sawdust could exhibit a high crude oil removal capacity of about 47 times the modified sawdust weight. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.