Catalytic supercritical water gasification (SCWG) for H-2 production is a hopeful way of coal conversion to replace the traditional coal utilization mode. At present, the detailed catalytic mechanism in the process remains unknown. Herein, a comprehensive catalytic SCWG mechanism of coal is proposed by establishing a novel catalytic kinetic model. It shows that catalysts (K2CO3) break up the coal matrix by a cyclic redox reaction to produce plenty of mesopores, accelerating steam reforming of fixed carbon and coal pyrolysis. Water-gas shift reaction is facilitated by K2CO3 via formation of formate, which then promotes steam reforming of CH4 at high temperature (>= 700 degrees C) due to the decreasing CO. The proposed mechanism provides important insights in catalytic SCWG process of coal. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.