Supercritical water partial oxidation (SCWPO) is a clean and efficient coal conversion method to produce H-2. However, the detailed SCWPO mechanism of coal is still unknown at present. In this paper, a lumped kinetic model is used to propose a non-catalytic SCWPO mechanism of coal. The results show that oxidation reaction of intermediate carbon is under diffusion control. Bituminous coal is harder to be gasified than lignite, due to the denser structure of bituminous coal. CH4 is produced only from coal pyrolysis, and it is negligible for steam reforming of CH4 without catalyst. The ash in coal plays a certain catalysis on water-gas shift reaction. The proposed mechanism provides important insights in SCWPO process of coal. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.