Abstract: The present disclosure provides a method for regulating a quality of an oil derived from plastic wastes by supercritical hydrothermal liquefaction, including catalyst synthesis, calcination, and supercritical hydrothermal liquefaction. In the present disclosure, a catalyst is prepared by the method, and then applied in regulating the quality of the oil derived from plastic wastes by supercritical hydrothermal liquefaction. This not only reduces cost, but also optimizes a reaction process, such that plastics can be recycled as resources, thereby reducing the carbon emissions and promoting the development of circular economy. The method has strong practicability and functionality, and can be widely used in the technical fields of harmless treatment and resource utilization of plastic waste.