The effects of industrial preheating and oxidation have been studied on four different vitrinite-rich coals of different rank. Raw, preheated, oxidized and preheated-oxidized coals were analyzed by three different pyrolysis techniques: Rock-Eval, pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and confined pyrolysis. Results indicate that gross and molecular parameters are modified during the different treatments. Oxidation induces a loss of oil potential and an increase of the thermostability while preheating is marked by a decrease of the Sigma aro/Sigma mono-aro ratio derived from Py-GC-Ms. Additional data show that preheated coals are more sensitive to oxidation than raw coals.