The performance of arsenic (As) poisoned catalysts in a 600 MW coal-fired power plant was tracked from 12/2013 to 10/2019, and the physicochemical characteristics and service lifetime of the catalyst at the initial stage, ultralow emission reconstruction stage, and catalyst replacement stage of deNO(x) device operation were investigated. The results revealed that the active components in the catalyst were lost over time, while the chemical components in the flue gas were gradually deposited on the catalyst. The deposition rate of As in the catalyst decreased with the increase in operation time and the three stages were 1245, 755, and 524 ppm/10(3) h, respectively. The specific surface area of the catalyst decreased to 1.57, 0.62, and 0.19 m(2)/(g.10(3)h) at the three stages, respectively, while the change rate of SO2/SO3 conversion and wall thickness at the three stages were linearly related to the operation time. Influenced by As poisoning and evolution in physicochemical characteristics, the decline rate of catalyst activity at the three stages was higher than the design value, which was 2.47, 5.11, and 2.76 m/10(4) h(2), respectively, resulting in the actual service lifetime of the catalyst of only 61, 65, and 52%, respectively.