To meet the increasing global energy demand and reduce the dependency on traditional fossil fuels, renewable biomass particularly cellulose has attracted considerable interest. Prior to processing and conversion into valuable products, cellulose needs to be pretreated (dissolved and then regenerated) via an environmentally benign route. Emerging as versatile solvents, ionic liquids (ILs) have been extensively examined for cellulose dissolution/regeneration. However, the underlying mechanisms of cellulose dissolution/regeneration in ILs remain elusive and the key governing factors are not fully understood at a microscopic level. This review summarizes the recent computational studies on cellulose pretreatment, including cellulose dissolution in neat ILs and IL/solvent mixtures, as well as cellulose regeneration by anti solvents Atom-resolution and time resolved insights are provided to microscopically and fundamentally elucidate cellulose dissolution/regeneration, which are indispensable in the rational screening and design of new ILs for efficient cellulose pretreatment. Furthermore, the challenges for future computational exploration in this field are discussed. (C) 2014 Elsevier Ltd. All rights reserved.