The peak position and intensity of three-dimensional fluorescence spectroscopy can be used to characterize the type and concentration of fluorescent substances, which is widely used in the study on dissolved organic matter (DOM) properties. In order to study the soil characteristics of different plant formations and guide the work of reverting farmland to wetland, the surface soil of six typical plant formations of Ulmus pumila, Salix sungkianica, Artemisia scoparia, Phragmites australis, Carex appendiculata, and Typha Orientalis were collected in this study, and the fluorescence spectroscopy of soil DOM was determined, the source and composition of soil DOM of the six plant formations were analyzed by three-dimensional fluorescence spectroscopy with parallel factor analysis method. Combined with physiochemical soil indexes, the influencing factors of soil DOM organic components were further analyzed. The results showed that there was no significant difference in the humification index of the six plant formations, the humification degree of the hygrophyte Phragmites australis formation was significantly higher than that of the xerophyte Artemisia scoparia formation. The fluorescence index of soil DOM was between the terrestrial eigenvalue (1.4) and the autochthonous eigenvalue (1.9), indicating that the source of soil DOM was not only generated by microbial activities, but also by the input of plant litter and root exudates. The fluorescence index and biological index of the soil in the Carex appendiculata formation and the Typha orientalis formation were relatively high, which indicated that the two formations had relatively strong autochthonous characteristics, while the terrestrial characteristics of the Phragmites australis formation and the Artemisia scoparia formation were relatively high. Three organic components, fulvic-acid-like component (C1), humic-acid-like component (C2) and protein-like component (C3), were identified from soil DOM of the six plant formations. The soil DOM relative concentration of Phragmites australis formation was higher than that of Typha orientalis formation, and that of Carex appendiculata formation was lower. Excepting for the Phragmites australis formation, C3 accounted for a relatively high proportion in the soil of each plant formation, followed by C1 and C2, which reflected that the surface soil DOM was relatively rich in small molecular substances, and indicated that the degree of humification was not high. There was no significant difference in soil pH value among different plant formations. The dry environment had higher soil bulk density, while the wet environment had higher soil water content and cation exchange capacity. The contents of soil total organic carbon, total N, total P and total K in woody plant formation were higher than those in herbaceous plant formation. Soil bulk density, water content and cation exchange capacity could significantly affect the soil DOM organic component structure. Therefore, increasing the area of hygrophyte herbage in the process of reverting farmland to a wetland can improve the degree of soil humification to a certain extent.