In accordance with the need of green and sustainable development, a magnetically recyclable solid catalyst was developed for the transformation of low-cost oils to biodiesel via simultaneous transesterification and esterifications in an efficient and environmentally benign manner. For this aim, the magnetic Fe3O4/SiO2 composites composed of iron oxides as the core and silica as the shell, were prepared, and then polymeric acidic ionic liquid (IL) was immobilized on the magnetic support through radical grafting copolymerization of Bronsted acidic IL, 1-vinyl-3-(3-sulfopropyl)imidazolium hydrogen sulfate, onto the magnetic support. The characterization results showed that the perfect core-shell structured Fe3O4/SiO2 support with good magnetic responsiveness was formed, and the polymeric acidic IL was tethered on the magnetic support. The combination of polymeric acidic IL with magnetic porous nanoparticles could enhance the catalytic activity and favored the separation performance of the catalyst. The solid catalyst exhibited high activities for both transesterification of soybean oil and esterification of free fatty acids generally presented in low-cost oils. Moreover, the catalyst could be simply recovered magnetically and efficiently reutilized for several times without significant loss in its activity, thus allowing its being potentially applicable for green and economic production of biodiesel especially from the low-cost oil feedstocks. (c) 2019 Elsevier Ltd. All rights reserved.