Phenolic wastewater comes mainly from coking, gas, and petrochemical plants, and other industrial sectors, as well as petroleum cracking ethylene, synthetic phenol, poly Thalidomide fibers, organic pesticides, and the phenolic resin production process. Phenolic compounds are monitoring our priority persistent organic compounds, having already been included in the column of carcinogenic single ring aromatics. In this paper, catalytic supercritical water gasification was applied to treat the phenolic wastewater. The influence of alkali on the gasification of phenolic wastewater with NaOH as catalyst at 580ºC, 27MPa was investigated. The results showed that the NaOH addition increased H2 fraction and gas yield. The reaction mechanism was analyzed.