Abstract: One technique using hydrogen donor was introduced for super heavy oil upgrading and reducing viscosity under steam injection in well. The main factors and rules in aqua-thermolysis reaction were analyzed through comparison of viscosity，asphaltene and sulfur content before and after super heavy oil upgrading. The results indicate that a certain content of sulfur existed in super heavy oil is one of the necessary conditions in aqua-thermolysis reaction at temperature of steam injection. Temperature and time have an important effect on aqua-thermolysis reaction. Among hydrogen donors tested, tetralin has the biggest effect on super heavy oil aqua-thermolysis. The combination of tetralin and catalyst of nickel sulphate has a synergetic function to the reaction. The physical simulation experiment of aqua-thermolysis under a certain condition shows that viscosity reduction ratio can reach about more than 70% after hydrogen donor catalytic aqua-thermolysis for the super heavy oil of Shengli Shanjiasi oilfield. The content of asphaltene, colloid and sulfur decreases, and H/C increases after upgrading process.