The catalytic effect of minerals on the hydrocarbon groups, viscosity, and element distribution of heavy oil during the thermal recovery process studied are in this paper. The results show that minerals have a catalytic effect in the aquathermolysis of heavy oil. When 10 wt% mineral was added to the reaction system, the saturate and aromatic content increased, while the resins and asphaltenes components decreased. The results also show that the average molecular weight of heavy oil and asphaltene was reduced after treatment, and the content of sulphur decreased. The viscosity of the heavy oil used in our study decreased by 23.4-25.6% in the reaction system after treatment with steam.