Supercritical water gasification (SCWG) can achieve efficient utilization of solid wastes, including depolymerization slag, biomass, municipal sludge, and others, and can produce hydrogen-rich gas. But phenolic intermediates produced during the gasification process are difficult to be gasified. It restricted the increase of conversion efficiency. Thus, in this paper, two effective schemes were put forward to raise the gasification efficiency of depolymerization slag. The first one was to add oxidants to promote the decomposition of hydrolysates. Carbon gasification efficiency (CGE) and hydrogen gasification efficiency (HGE) reached 71% and 74% respectively at the time of 1200 s. They raised by 41.6% and 60.5%, separately compared with non-oxidants addition. The second one was to raise the reaction temperature since a higher temperature can accelerate the reaction rate and obtain a high hydrogen yield. The results showed that hydrogen percentage increased by 32.82% and CGE and HGE increased by 35.39% and 219.85%, respectively when the reaction temperature raised by 200 degrees C. Based on the obtained gasification mechanism, the catalytic gasification. (c) 2020 Elsevier Ltd. All rights reserved.