Abstract: Taking the SCR denitrification catalyst under the data lake of a coal-fired power plant as an example, the change rules of the physicochemical properties and the catalyst denitrification performance were comprehensively analyzed by on-site investigation, catalyst indicator testing, etc. The results showed that under certain coal and flue gas conditions, the mechanical strength index of the catalyst was not easily affected by the environment in the reactor within the unit utilization time, and the compressive strength detection value remained almost unchanged. The dust in the flue gas and the reaction products helped enhance the catalyst’s attrition resistance. However, with the extension of utilization time, the catalyst would experience structural damage such as inner wall cracks, thinning of wall thickness, and wear through of pore walls, which was not conducive to the safe and stable operation of the catalyst. Some major chemical components (TiO₂, V₂O₅, WO₃), trace elements (Na, K, Fe, As), specific surface area, denitrification efficiency, and SO₂/SO₃ conversion rate all showed a downward trend, while some other major chemical components (SiO₂, Al₂O₃, CaO) showed an upward trend, which indicated that the physicochemical and process indicators of the catalyst were greatly affected by the internal environment of the reactor, resulting in negative effects on each indicator and affecting the overall performance of the catalyst. By analyzing the attenuation law or key factors of the chemical and mechanical indicators of SCR catalysts under flue gas conditions, the research can provide a theoretical reference for the entire process management of catalysts.