Novel magnetic carbon based solid acid has been synthesized through the hydrothermal carbonization of glucose with magnetic cores and sulfonation of carbonaceous intermediate with hydroxyethylsulfonic acid. The carbon based solid acid owned the core-shell structure and high BET surface, which provided the easily accessible acid sites on the shell. The magnetic solid acid exhibited high activities for the hydrophobic alkylation of benzene and dodecene with complete conversion of dodecene, which was difficult for the traditional carbon based acids for low hydrophilic surface. The simple magnetic recovery process and high stability added the advantages of the solid acid. The high activities, reusability and simple recovery process were the key properties of the solid acid, which hold great potential for green chemical processes. (C) 2014 Elsevier B.V. All rights reserved.