Abstract: The control of the actual operating performance of the catalyst is critical to the stable operation of SCR denitrification system. In this paper, the fresh catalyst and used catalyst after different time periods of operation in a power plant were taken as the research objects. The physical and chemical properties, mechanical properties, and microstructure of catalyst are tested, and its impact on the operation of the catalyst is analyzed. Through the study on the process characteristics and activity of the catalyst in operation, it is expected that the catalyst performance test will provide the basis for the replacement and installation of the denitration catalyst. The results show that after the catalyst having been installed and used for more than two years in the coal-fired power plant, operational risk has increased to certain level with the escaping rate of ammonia approaching the upper limit of the guaranteed value . In order to ensure the safe and efficient operation of the denitrification system, the catalyst management should be actively involved after being put into service.