Thermal degradation behavior of a WO3-TiO2 monolithic catalyst was investigated in terms of structural, morphological, and physico-chemical analyses. The catalyst with 4 wt.% WO3 contents were prepared by a wet-impregnation method, and a durability test of the catalysts were performed in a temperature range between 400℃ and 800℃ for 3 h. An increase of thermal stress decreased the specific surface area, which was caused by grain growth and agglomeration of the catalyst particles. The phase transition from anatase to rutile occurred at around 800℃ and a decrease in the Brønsted acid sites was confirmed by structural analysis and physico-chemical analysis. A change in Brønsted acidity can affect to the catalytic efficiency; therefore, the thermal degradation behavior of the WO3-TiO2 catalyst could be explained by the transition to a stable rutile phase of TiO2 and the decrease of specific surface area in the SCR catalyst.