Display omitted •NO oxidation of SmMn2O5 is studied via first-principles based microkineitc models.•MvK and ER mechanisms separately contribute to high activity of pristine SmMn2O5.•Ba doping destabilizes NO∗ species for high reaction activity along MvK route.•Sr and La doping enhance the O2∗ dissociation for high reactivity via ER pathway. Using first-principles based microkinetic analysis, we conduct a comprehensive investigation on the NO oxidation process on SmMn2O5 mullite’s active surface under experimentally relevant conditions. The influencing factor for NO oxidation activity is identified and Mars-van Krevelen (MvK) and Eley-Rideal (ER) mechanisms are found to contribute to the high activity of pristine SmMn2O5 mullites in high and low temperature regions, respectively. We further study the activity of surface (Ba/Sr/La) doped SmMn2O5. It is found that surface doping of Ba primarily destabilizes the nitrite (NO∗) species to promote NO oxidation performance via MvK mechanism. Due to the stronger ability of O2 (O2∗) dissociation along the ER route, Sr and La doped mullites are predicted to have greatly enhanced reaction activity in a wide temperature region. Our study gives insight into the NO oxidation ability of pristine and surface doped SmMn2O5 that are beneficial for further optimization of mullite based catalyst performance.