Nitrogen oxides, as one of the main atmospheric pollutants, cause potential risks to human health and the atmospheric environment. In recent years, nitrogen oxide emissions from power plants have been reduced, and controlling nitrogen oxide pollution in non-electric industries and emerging power generation sectors, such as waste incineration power generation and biomass combustion power generation, has become the focus of flue gas emission control from stationary sources. Currently, the most widely used and effective technology for nitrogen oxide purification is Selective Catalytic Reduction (SCR) using ammonia. The complex working conditions of flue gas purification technology for non-electric industries and emerging power generation sectors often result in the presence of large amounts of H_2O, acidic gases (SO_2, HCl), alkali/alkali earth metals (Na, K, Ca), heavy metals (Pb, Cd, As), and phosphorus compounds in the flue gas. These components can lead to catalyst poisoning and severe deactivation. To address the deactivation issues of nitrogen oxide purification catalysts during practical application, researchers have conducted extensive studies on improving SO_2 tolerance, alkali metal and alkali earth metal resistance, and resistance to multiple poisons under complex flue gas conditions. This paper reviews recent research on nitrogen oxide catalytic purification technology for flue gas under complex conditions and summarizes strategies to improve resistance to SO, poisoning, alkali metal poisoning, and multiple poisoning. This review provides guidance and strategies for the development of efficient, stable and anti-poisoning nitrogen oxide purification catalysts. At the same time, it offers a theoretical foundation for promoting the practical application of nitrogen oxide purification catalysts in the complex flue gas purification from non-electric industries and emerging power generation sectors.