Various experiments and analyses were performed to explore the reasons for SO2 durability enhancement of the V/TiO2 catalyst, which was created by the ballmill (BM) method. Compared to the BM catalyst, the raw catalyst showed low selective catalytic reduction (SCR) activation in mid/low temperature ranges. As the raw catalyst’s SCR activity in low temperature range was lower than the BM catalyst’s activity, the amount of unreacted NH3 emitted was higher. However, in the presence of SO2, the emitting amount of unreacted NH3 was decreased. According to BET and FT-IR analysis, this phenomenon occurs due to the relatively high production of ammonium sulfate salts, which are created by unreacted ammonia and water in response to the presence of SO2. However, the BMcatalyst emits less unreacted ammonia due to its excellent SCR activity. Moreover, when the SCR experiment at each level of water concentration was performed, water adsorption to the catalyst’s active site occurred less frequently. According to the XPS analysis, the BM catalyst includes a great amount of non-stoichiometric chemical species V^(x+) (x ≤ 4). This means that the BM catalyst provokes less oxidation of SO2 to SO3. Therefore, the BM catalyst shows excellent SO2 durability.