under the“Carbon Peaking and Carbon Neutrality”target，traditional steam injection thermal recovery methods such as steam huff -puff and steam flooding exist in a series of problems such as high cost，high energy consumption and high carbon emissions. It is urgent to find new technologies to improve the development effect. Catalytic aquathermolysis of heavy oil is an effective technology for its recovery and has achieved significant developments in recent years. In the article，the Q40 block heavy oil in Liaohe oilfield was taken as the research object，the indoor high-temperature catalytic aquathermolysis reaction of heavy oil was conducted at different temperatures，time and concentrations of nano-copper based catalyst systems using high-temperature and high-pressure reactors indoors. By measuring the viscosity，group composition，and gas composition of the crude oil before and after the reaction，the viscosity reduction and upgrading effect and mechanism were systematically studied. The experimental results showed that the reducing viscosity and upgrading effect could not be achieved relying solely on high-temperature treatment. The addition of nano-copper based catalyst system had the reducing viscosity and upgrading effect on crude oil. As the concentration and reaction time of the reagent system increased，the viscosity of crude oil decreased after the high-temperature reaction，the content of saturated hydrocarbons and aromatics in the light components of crude oil significantly increased，and the content of asphaltene and gum in the heavy components significantly decreased. When the catalyst concentration increased from 0.3% to 0.75%，the viscosity of the crude oil after the reaction decreased from 1899 mPa·s to 1164 mPa·s，and the viscosity reduction rate increased by 7.3%. The viscosity of crude oil samples subjected to high-temperature reaction for 3 days decreased by 49.5% compared to those subjected to high-temperature reaction for 0.5 days. The reaction temperature had a relatively small impact on the effectiveness of the catalytic system. After high-temperature catalytic aquathermolysis reaction at 180 ℃，the viscosity of crude oil decreased from 10 940 mPa·s of the base oil sample to 1765 mPa·s，with a viscosity reduction rate of 83.9%. The viscosity of crude oil after reaction at different temperatures（180—260 ℃）had little difference，especially when the reaction temperature exceeded 200 ℃， the viscosity reduction rate of crude oil changed little. The nano-copper based catalyst system has strong temperature adaptability， wide effective temperature range，good reducing viscosity and upgrading effect on heavy oil.