This paper studied the distribution and occurrence of elements in fresh and deactivated catalysts with operational time of 35000 h, which were used in flue gas denitration process in thermal power plant. At gas hourly space velocity of 30000 h?1, NH3 to NO volume ratio of 0.8, and 5 vol% O2, NO conversion rate was only 41% at 200 °C using the deactivated catalyst, and it decreased 8% compared with the fresh catalyst at the temperature of 250 to 400°C. The main phase of deactivated catalyst remained the anatase TiO2, but the honeycomb structure of deactivated catalyst was destoried. Due to the surface chemical erosion, the size of TiO2 particles decreased to 37.2 nm. The impurity elements, such as Fe, K, Al, and As, have heterogeneously deposited on the surface of the catalyst. It results in 10.44% decreasing of total pore volume. Compared with the fresh catalyst, the distribution of anatase TiO2 becomes heterogeneous in the deactivated catalyst. The atomic ratio of V/Ti reduced by 29.53%, and the valence ratio of V4+/(V4++V5+) also reduced by 25.89%. It leads to the decreasing of the acid site on the surface, and the activity of catalyst obviously decreased at low temperatures.