Dissolved organic matter (DOM) is a substance characterized by a variety of structural compositions, complex physicochemical properties and a wide molecular weight distribution. It is composed primarily of humic acids, fulvic acids, proteins, lipids and other organic components, as well as carboxylic acids, hydroxyl, phenolic, aldehyde and other reactive groups. DOM is ubiquitous in lake ecosystems, where it participates in a variety of biogeochemical processes. These processes influence the migration, transformation and behavior of biotic elements and pollutants, and play an important role in the conversion of carbon sinks in ecosystems. DOM in lake water exhibits a variety of environmental behaviors. For instance, DOM can be adsorbed to the surface of water particles, and the distribution of DOM in the dissolved/suspended phase can be regulated; DOM in lakes will undergo photo-and microbial degradation, which will change the content and structural composition of DOM samples; the multifunctional groups in DOM in lakes can be easily complexed with metal ions, and can also undergo electron transfer to produce reactive oxygen species. Furthermore, the existence of DOM in lakes has been proven to have substantial ecological and environmental impacts. Specifically, DOM in colloidal particles significantly influences the stability of these colloids and the transparency of the surrounding water. Moreover, the binding of DOM with heavy metals can change the bioavailability of these metals, thus influencing the well-being of lake ecosystems. Additionally, DOM in lakes can either facilitate the degradation of organic pollutants via reactive oxygen species mediation or impede this process by acting as a light shield. It is crucial to emphasize that the behavior and ecological effects of lake DOM are intricately linked to its molecular weight, active groups, and molecular structure. In this paper, we conduct a comprehensive and systematic review of the behavior and ecological effects of lake DOM, as well as its correlation with molecular structure composition. The findings of this review can offer valuable theoretical guidance and technical support for understanding the processes and mechanisms of lake pollution, implementing lake restoration and regulation measures, and formulating lake management and planning strategies.