In order to investigate the synergistic catalytic aquathermolysis after external catalyst entering the reservoir and complexation with in?situ inorganic minerals,a simulated internal and external synergistic catalyst of montmorillonite?supported zinc citrate complex was prepared,and its catalytic viscosity reduction performance for heavy oil was investigated.The heavy oil before and after the reaction was analyzed by thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),gas chromatography(GC) and elemental analysis(EA).The results showed that the composite catalyst B@Zn(Ⅱ)L increased the viscosity reduction rate of heavy oil from 55.2% to 65.4% at 30 ℃,which confirmed the phenomenon of internal and external source synergistic catalysis in heavy oil thermal recovery.After synergizing the composite catalyst B@Zn(Ⅱ)L with the hydrogen supply agent ethanol,the viscosity reduction rate of heavy oil increased from 65.4% to 80.1%.After the reaction of heavy oil, some of the high hydrocarbon compounds in the heavy oil were cracked into low hydrocarbon compounds after the reaction,and some heavy components were decomposed into light components.Therefore, the wax precipitation point of heavy oil decreased,the mass fraction of N and S decreased,the content of high hydrocarbons decreased,and the content of low carbon hydrocarbons increased.