Chemical looping oxidative coupling of methane (CLOCM) is an energy-saving approach for C2 products. Despite efforts to oxygen carriers(OCs) modification by metal dopants or plasma assistance, the intrinsic oxygen amount and migration resistance limit the C2 yield below the industrial requirement. In this work, CO2-mediated Mg6MnO8 modification is introduced into CLOCM. Considering the raw feed for future industrial applications, biogas involving CH4 and CO2 was used. Simulated biogas with 50%–65% CH4 and 35%–50% CO2 is investigated at 800°C and atmospheric pressure. CO2 contributes to the enhancement of CH4 conversion and C2 selectivity, delivers monoatomic oxygen species, and increases the oxygen transfer capacity. The enhanced oxygen transfer and CO2's function as the limiting reactant reinforce CH4 activation and H abstraction. The enhanced C2 selectivity is due to the fact that the process of CO2 adsorption and activation on Mg6MnO8 surface reduces the reaction exothermicity and suppresses the undesirable oxidation products, and that CO2 doesn't react with CH3* radicals. However, excessive CO2 addition may lead to the generation of peroxycarbonate intermediates and reduce the ability to further boost C2 selectivity. These suggest that CO2 acting as a gas-mediated modification of OCs and biogas as the raw feed in the CLOCM process efficiently produce C2. The ideal biogas is 60% CH4 and 40% CO2, increasing C2 selectivity and yield by 2 times and 1.5 times, respectively. These discoveries offer a new method for C2 products and the integration of biogas usage with CLCOM, responding to the worldwide call for carbon neutrality.