For increasing active ingredients accessibility to the solvents, microwave assisted ionic liquid pretreatment (MILP) is introduced to destroy cell walls of medicinal plants before solvent extraction. As a new sample pretreatment method, microwave irradiation on sample pretreatment with ionic liquids (ILs) was investigated. The conditions of MILP including microwave pretreatment time and power, ionic liquid (IL) and sample ratio and particle size were optimized and Cynanchum paniculatum and its active ingredient paeonol were chosen as the representative target analyte. Under the optimized conditions, the paeonol extraction yield by MILP was higher than that of ionic liquid aqueous solution and Soxhlet extraction. In addition, the results of bioassay test showed that the antibacterial effect of crude extract by MILP was almost the same with that of soxhlet extraction. Our results demonstrate that sample pretreatment with ILs and microwave irradiation is a potential alternative method for the pretreatment of medicinal plants before solvent extraction. (C) 2011 Elsevier B.V. All rights reserved.