The (001) surface of TiO2 is proved to be more active than the (101) surface in the SCR reaction while the roles of these two surfaces were still unclear. The present study carefully compared the adsorption characteristics of the (001) and (101) surfaces of original and MnO2-loaded anatase by density functional theory calculations. The oxidizing ability and the feasibility of the oxygen vacancy formation were further explored. It was found that NH3, NO, NO2 and O-2 tended to adsorb on the (001) surface rather than on the (101) surface and the (001) surface was more oxidizing and was more prone to generate oxygen vacancies. Loading MnO2 had a significant promotion on the performance of the (001) surface. The adsorption performance of the Mn(001) surface was much better than that of the Mn(101) surface. The limiting reactions for N-2 and H2O production on the Mn(001) and Mn(101) surfaces were both the dissociation process of NH3. The energy barriers of the SCR reaction on the Mn(001) surface were smaller than that on the Mn(101) surface, indicating that N-2 and H2O formation on the Mn(001) surface was easier.