Abstract: In this study, density functional theory was used to explore the effects of different nitrogenous biochars and CaO-coupled nitrogen-doped biochar on the adsorption performance of NO. The theoretical calculation results showed that nitrogen-doped biomass char had a better adsorption effect on NO under N-down adsorption mode, and the adsorption energy of N-5 biomass char (CN-5) was higher than that of nitrogen-containing biochar, and its adsorption energy was −41.22 kJ/mol. CaO significantly improved the adsorption capacity of biochar to NO, and CaO coupled with the substrate containing N-5 biochar (CaO/CN-5) as an electron donor provides more charge for NO, and its adsorption energy was 216.862 kJ/mol higher than that of CN-5, and the adsorption performance of biochar was significantly improved under the coupling of CaO and N-5 groups. The adsorption capacity of NO on the surface of biochar decreased with the increase of temperature, and increasing the amount of biochar containing N-5 was more conducive to the adsorption of NO, while the coupling of CaO further increased the adsorption capacity of NO-5 surface NO, and the adsorption capacity of CaO/CN-5 system reached 2.846 mmol/g at 273 K.