The Gaoqing-Pingnan fault is the primary pathway of mantle-derived fluids flow in the Dongying sag. The mantle-derived fluids consist of magma and CO2. There are temporal and spatial differences in the flow pattern and activity intensity of the mantle-derived fluids in the Gaoqing-Pingnan fault. It has experienced at least 4 times of CO2-rich mantle-derived fluids flow in the Gaoqing-Pingnan fault during the Tertiary. The influences of the CO2-rich mantle-derived fluids on oil-gas reservoir formation in the Gaoqing-Pingnan fault are: (1) to form directly inorganic CO2 reservoirs; (2) to influence the direction and intensity of water-rock interaction and improve the porosity and permeability of the reservoir by the input of energy (i. e. heat action) and material (i. e. CO2); (3) to improve the expulsion efficiency of source rocks and increase oil and gas migration velocity.