At present,there are many adsorption materials,such as zeolite,MOFs,polymers,etc,while biomass has the advantages of widedistribution,low cost,renewable and net zero emissions,which has become a research hotspot. Previous studies have shown that nitrogendoping is beneficial to improving the CO2 adsorption performance of biocha,and biochar can be modified by metal minerals to increase theeffective adsorption area of biochar surface. However,it is still not clear which nitrogen groups significantly affect the CO2 adsorption performance on the surface of biochar. The adsorption characteristics of CO2 on the surface of biochar under the synergistic effect of metallic minerals and nitrogen-rich modification are not yet clear. Based on this,quantum chemistry theory was used to calculate and study theadsorption mechanism of CO2 on the surface of biochar with different nitrogen-containing groups,and the influence mechanism of different metal oxides (MgO,CaO) and their coupled nitrogen-doped biochar on CO2 adsorption was systematically explored. The results showthat biochar containing N-X has the strongest adsorption effect on CO2 among the different adsorption methods of nitrogen-containing biochar. By analyzing the three different adsorption modes of CO2 in MgO and CaO systems,namely O-Top,Hollow,and Bridge,it is concluded that the adsorption energy of CO2 in O-Top mode on CaO system is the maximum,and the adsorption energy of CO2 in O-Top mode is92.22 kJ/ mol higher than that in MgO under the same adsorption mode. Compared with MgO,O in CaO has a stronger effect on C in CO2,with more overlapping electron clouds,more charge transfer,and stronger gravitational attraction between CaO and CO2 molecules. Furtherstudy show that the coupling of N-X biochar and CaO has a certain synergistic promoting effect on the adsorption of CO2. Compared withN-X biochar and CaO alone,the adsorption energy of CO2 by the coupling of the two increases by 136.81 kJ/ mol and 0.87 kJ/ mol,respectively. This study provides theoretical support for the preparation of high quality carbonaceous chemicals.