Abstract: The hydrocracking of Gudao residue in supercritical water using different hydrocracking media (CO+H2/H2O, CO/H2O, H2/H2O, H2) and in situ generated hydrogen from water gas shift reaction(WGSR)in the presence of dispersed catalyst precursor phosphomlybdic acid (PMA) was investigated. The results show that catalytic hydro-con-version of Gudao residue using in situ generated hydrogen is an effective upgrading technology for heavy oil. In situ generated hydrogen from WGSR is more reactive than the supplied molecular hydrogen for residue hydro-conversion. Under the proper reaction conditions, the hydro-conversion of residue in supercritical water-syngas system is similar to hydro-conversion of residue with the supplied molecular hydrogen.