Abstract: Constructed wetlands are complex ecological treatment systems, and their pollutant purification process is the combined effect of physical, chemical and biological processes. However, the types and concentrations of pollutants in wastewater from different sources vary significantly, resulting in complexity and differences in the pollutant removal effect and mechanism of constructed wetlands, which restricts the promotion and application of constructed wetland technology. This review summarizes the research results on the treatment of industrial, agricultural and domestic wastewater from different sources by constructed wetlands. It concludes that the pollutants that can be treated include nutrients, organic matter, heavy metals, emerging pollutants, fluorides, sulfates and chlorides, among which the proportion of research literature related to domestic wastewater is as high as 64.45%. Pollutants are mainly concentrated in nitrogen, phosphorus and organic matter. The purification mechanisms of each functional unit of constructed wetlands are mainly summarized as follows: (1) Microorganisms remove nitrogen and organic matter through degradation and transformation processes. (2) The filler matrix removes phosphorus, heavy metals and fluorides through filtration, adsorption, sedimentation and ion exchange, etc. (3) Plants, while providing a living environment for microorganisms, also participate in the absorption and transformation of pollutants. (4) For petroleum and new pollutants, it relies on the biodegradation of domesticated microorganisms and the assistance of plants in absorption. The removal of sulfates also depends on the synergistic action of sulfur-metabolizing microorganisms such as sulfate-reducing bacteria and sulfur-oxidizing bacteria. In actual wastewater, there often exists complex pollution problems where multiple pollutants such as nitrogen, phosphorus, organic matter, and heavy metals coexist. Traditional constructed wetland systems still lack a systematic understanding of the collaborative removal mechanism of multiple pollutants. In the future, constructed wetland systems suitable for complex pollution scenarios can be constructed to enhance their collaborative purification capacity and anti-shock performance. Although some pollutants such as petroleum hydrocarbons and new pollutants can be effectively removed in wetlands, their transformation pathways and final products during the treatment process are still unclear. It is necessary to strengthen the quantitative detection and toxicological assessment of the transformation products of such pollutants after treatment. In constructed wetlands, microorganisms, plants and fillers play a synergistic role in the process of pollutant removal. However, at present, there is a lack of quantitative and mechanistic understanding of their respective contributions and the coupling mechanisms in multiple media and processes. Future research should focus on the analysis and optimal regulation of multi-component interaction processes to provide theoretical support for the structural design and functional improvement of constructed wetlands. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202504290110.