A new method is presented to study the structure and reactivity of coal by solvent swelling technology, Four different rank coals are swollen by the use of N-methylpyrolidinone (NMP) under mild condition. Heat effect changes are demonstrated with differential scanning calorimetry (DSC) before and after the solvent swelling. Swollen coal volatile yields increase with the extent of coal swelling ratio (Q). During the swollen coal pyrolysis under the condition of 20 degrees C/S to 1100 degrees C, the activation energy of functional groups in coal structure is decreased. Furthermore, pyrolysis Fourier transform infrared spectroscopy (PY-FTIR) data show that the gasification reactivity of coal char has been improved. Thus, coal macromolecular structure becomes sufficiently flexible and will irreversibly be rearranged by good nucleophilic solvent pretreatment. Coal forms a lower energy conformation after the removal of solvent. (C) 2000 Elsevier Science B.V. All rights reserved.