The grafting copolymerization of maleic anhydride (MAH) onto ticrylonitrile-butadiene-styrene terpolymer (ABS) was carried out through solvothermal process. Infrared (IR) spectra and H-1 NMR spectra confirmed that maleic anhydride was successfully grafted onto the ABS backbone. The influences, such as MAH concentration, the initiator's content, reaction temperature and time, comonomer, ABS concentration and different solvents, on the grafting copolymerization were also studied. Results indicated that the preparation of MAH grafted onto ABS through solvothermal method can be carried out in both good solvent and poor solvent, which is much different from the traditional solution grafting method, and high grafting degree call be obtained in good solvent. © 2005 Elsevier Ltd. All rights reserved.