TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAquathermolytic technology that involves upgrading heavy oil using chemical additives is introduced in this paper. Laboratory experiments were carried out under steam injection conditions to investigate catalysis of some metal species and synergetic effect of catalyst and hydrogen donor on aquathermolysis of Liaohe and Shengli heavy oils. As a result, significant reduction in viscosity and contents of asphaltene and resin was obtained, thus heavy oils were upgraded greatly. Then the mechanism of aquahtermolysis is discussed further. Additionally, the field test in Liaohe Oifield is introduced. The future is suggested in the end.