Biochar has an important potential to alleviate ammonia (NH₃) volatilization and nitrous oxide (N₂O) emission from farmland, but there is often an "aging" phenomenon after biochar enters the environment, which brings uncertainty to the long-term effectiveness in alleviating global warming. To explore the long-term effect of biochar, a variety of aging factors such as water, temperature, oxygen, soil minerals, and microorganisms in nature were artificially accelerated, combined with multiple characterization methods to compare the effects of different aging methods on the properties of biochar, and used the principal component analysis (PCA) method to establish new comprehensive indicators of biochar properties to reflect the aging intensity. Through field experiment, the effects of aged biochar application on NH₃ volatilization and N₂O emission from summer maize planting farmland were monitored by in-situ ventilation and static chamber-gas chromatographic techniques, providing scientific evidence for the sustainable application of biochar. The results showed that the aging process increased the oxygen content, specific surface area (S_BET), total pore volume (V_t), and the number of oxygen-containing functional groups of biochar (BC), while reduced the ash, pH, carbon content, average pore diameter, and aromaticity. The aging intensity was ranked as follows: oxidation aging biochar (OBC)>mineralized aging biochar (KBC)>microbial aging biochar (MBC)>wet-dry cycle aging biochar (WBC) >freeze-thaw cycle aging biochar (FBC)>BC. The addition of biochar reduced the NH₃ volatilization by 13.57%-29.50%. Compared with BC, OBC and KBC significantly reduced NH₃ volatilization by 14.71% and 9.38%, respectively (P<0.05), while MBC reduced NH₃ volatilization by 3.38% (P>0.05). On the contrary, WBC and FBC increased NH₃ volatilization by 4.55% and 2.72%, respectively (P>0.05). At the same time, the addition of biochar reduced N₂O emissions by 22.36%-40.43%. Among them, BC had the best emission reduction effect, and aging has weakened the emission reduction effect of raw biochar on N₂O. Compared with BC, OBC and KBC significantly increased N₂O emissions by 30.34% and 26.36% (P<0.05), while MBC, FBC and WBC increased N₂O emission by 19.96%, 18.29% and 10.92%, respectively (P>0.05). In summary, different aging methods can cause different changes in the properties of biochar, thereby affecting the release of soil gaseous nitrogen. By comparing different aging methods, OBC had the most significant impact, followed by KBC, with MBC in the middle, and WBC and FBC had the weakest impact.