Abstract: To reveal the spatio-temporal evolution characteristics and influencing factors of dissolved organic matter (DOM) in sediments from plateau wetland - Guizhou Caohai during different water periods, ultraviolet-visible absorption spectrum (UV-Vis), three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy, and parallel factor analysis (PARAFAC) were used to analyze the DOM content, source, molecular properties, and fluorescence components in sediments from Caohai during dry and wet periods to provide a theoretical basis for understanding substance cycling and aquatic ecological protection in plateau wetlands. The results showed that DOM concentration in sediments ranged from 0.79 to 5.14 mg/g, and it contained two fluorescence components: protein-like (C1) and humus-like (C2), among which C1 was the dominant component with the average fluorescence intensity of 78.01%. The DOM was predominantly composed of fulvic acids, exhibiting weak humification characteristics and a combination of endogenous and terrigenous origins with high bioavailability. The content, relative concentration, degree of humification, aromaticity, and number of functional groups of DOM in sediments were lower in the wet season than in the dry season, while the autogenetic characteristics were stronger in the wet season. The high fluorescence intensity of fluorescence components was observed in the central and northeastern area of Caohai during the dry season, which might be related to the topography of Caohai Lake and human activities in the northern cities. The C2 component concentrated in the southern lakeside area in the wet season, probably due to agricultural runoff in the southern Caohai. Correlation analyses, co-occurrence network, and Mantel test showed that the TOC, TP and CAT enzyme activity were significantly correlated with DOM components. Human activities and microbial processes influenced DOM characteristics in the dry season, whereas it might also be affected by more factors such as wind-wave disturbance and photodegradation in the wet season. The study showed that the DOM in Caohai sediments was dominated by protein-like components, exhibiting weak humification characteristics and favorable biochemical availability, indicating a potential risk of algae bloom outbreaks.