Dissolved organic matter (DOM) is a kind of substances with various structural compositions, complex physicochemical properties and wide molecular weight distribution, which mainly contains humic acids, fulvic acids, proteins, lipids and other organic components, as well as carboxylic acid, hydroxyl, phenolic, aldehyde and other reactive groups, etc. DOM exists widely in lake ecosystems, and it can participate in a variety of biogeochemical 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 has various environmental behaviors. For example, 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. In addition, lake DOM also has significant ecological and environmental effects. DOM can be loaded on the surface of colloidal particles, affecting the stability of colloidal particles and transparency of the water body; DOM binding with heavy metals will change the bioavailability of heavy metal and the health of lake ecosystems; lake DOM can promote organic pollutant degradation through the mediating role of reactive oxygen species, or inhibit pollutant degradation through the role of light shielding. It should be pointed out that the behavior and ecological effects of lake DOM are closely related to its molecular weight, active group and molecular structure. In this paper, we systematically review the behavior and ecological effects of lake DOM and its correlation with the molecular structure compositions. Results obtained can provide theoretical guidance and technical support for the process and mechanism of lake pollution, lake restoration and regulation, lake management and planning.